diff --git a/keyserver/src/responders/website-responders.js b/keyserver/src/responders/website-responders.js
index e4eb2bdfc..b7607a5e5 100644
--- a/keyserver/src/responders/website-responders.js
+++ b/keyserver/src/responders/website-responders.js
@@ -1,836 +1,845 @@
 // @flow
 
 import html from 'common-tags/lib/html/index.js';
 import { detect as detectBrowser } from 'detect-browser';
 import type { $Response, $Request } from 'express';
 import fs from 'fs';
 import _isEqual from 'lodash/fp/isEqual.js';
 import _keyBy from 'lodash/fp/keyBy.js';
 import * as React from 'react';
 // eslint-disable-next-line import/extensions
 import ReactDOMServer from 'react-dom/server';
 import t from 'tcomb';
 import { promisify } from 'util';
 
 import { inviteLinkUrl } from 'lib/facts/links.js';
 import { baseLegalPolicies } from 'lib/facts/policies.js';
 import stores from 'lib/facts/stores.js';
 import { daysToEntriesFromEntryInfos } from 'lib/reducers/entry-reducer.js';
 import { freshMessageStore } from 'lib/reducers/message-reducer.js';
 import { mostRecentlyReadThread } from 'lib/selectors/thread-selectors.js';
 import { mostRecentMessageTimestamp } from 'lib/shared/message-utils.js';
 import {
   threadHasPermission,
   threadIsPending,
   parsePendingThreadID,
   createPendingThread,
 } from 'lib/shared/thread-utils.js';
 import { defaultWebEnabledApps } from 'lib/types/enabled-apps.js';
 import { entryStoreValidator } from 'lib/types/entry-types.js';
 import { defaultCalendarFilters } from 'lib/types/filter-types.js';
 import { keyserverStoreValidator } from 'lib/types/keyserver-types.js';
 import { inviteLinksStoreValidator } from 'lib/types/link-types.js';
 import {
   defaultNumberPerThread,
   messageStoreValidator,
 } from 'lib/types/message-types.js';
 import { defaultEnabledReports } from 'lib/types/report-types.js';
 import { defaultConnectionInfo } from 'lib/types/socket-types.js';
 import { threadPermissions } from 'lib/types/thread-permission-types.js';
 import { threadTypes } from 'lib/types/thread-types-enum.js';
 import { threadStoreValidator } from 'lib/types/thread-types.js';
 import {
   currentUserInfoValidator,
   userInfosValidator,
 } from 'lib/types/user-types.js';
 import { currentDateInTimeZone } from 'lib/utils/date-utils.js';
 import { ServerError } from 'lib/utils/errors.js';
 import { promiseAll } from 'lib/utils/promises.js';
 import { defaultNotifPermissionAlertInfo } from 'lib/utils/push-alerts.js';
-import { infoFromURL } from 'lib/utils/url-utils.js';
+import { infoFromURL, urlInfoValidator } from 'lib/utils/url-utils.js';
 import {
   tBool,
   tNumber,
   tShape,
   tString,
   ashoatKeyserverID,
 } from 'lib/utils/validation-utils.js';
 import getTitle from 'web/title/getTitle.js';
 import { navInfoValidator } from 'web/types/nav-types.js';
 import { navInfoFromURL } from 'web/url-utils.js';
 
 import { fetchEntryInfos } from '../fetchers/entry-fetchers.js';
 import { fetchPrimaryInviteLinks } from '../fetchers/link-fetchers.js';
 import { fetchMessageInfos } from '../fetchers/message-fetchers.js';
 import { hasAnyNotAcknowledgedPolicies } from '../fetchers/policy-acknowledgment-fetchers.js';
 import { fetchThreadInfos } from '../fetchers/thread-fetchers.js';
 import {
   fetchCurrentUserInfo,
   fetchKnownUserInfos,
   fetchUserInfos,
 } from '../fetchers/user-fetchers.js';
 import { getWebPushConfig } from '../push/providers.js';
 import { setNewSession } from '../session/cookies.js';
 import { Viewer } from '../session/viewer.js';
 import { streamJSON, waitForStream } from '../utils/json-stream.js';
 import {
   getAppURLFactsFromRequestURL,
   getCommAppURLFacts,
 } from '../utils/urls.js';
-import { validateOutput } from '../utils/validation-utils.js';
+import { validateOutput, validateInput } from '../utils/validation-utils.js';
 
 const { renderToNodeStream } = ReactDOMServer;
 
 const access = promisify(fs.access);
 const readFile = promisify(fs.readFile);
 
 const googleFontsURL =
   'https://fonts.googleapis.com/css2?family=IBM+Plex+Sans:wght@400;500;600&family=Inter:wght@400;500;600&display=swap';
 const localFontsURL = 'fonts/local-fonts.css';
 async function getFontsURL() {
   try {
     await access(localFontsURL);
     return localFontsURL;
   } catch {
     return googleFontsURL;
   }
 }
 
 type AssetInfo = {
   +jsURL: string,
   +fontsURL: string,
   +cssInclude: string,
   +olmFilename: string,
   +commQueryExecutorFilename: string,
   +opaqueURL: string,
 };
 let assetInfo: ?AssetInfo = null;
 async function getAssetInfo() {
   if (assetInfo) {
     return assetInfo;
   }
   if (process.env.NODE_ENV === 'development') {
     const fontsURL = await getFontsURL();
     assetInfo = {
       jsURL: 'http://localhost:8080/dev.build.js',
       fontsURL,
       cssInclude: '',
       olmFilename: '',
       commQueryExecutorFilename: '',
       opaqueURL: 'http://localhost:8080/opaque-ke.wasm',
     };
     return assetInfo;
   }
   try {
     const manifestString = await readFile('../web/dist/manifest.json', 'utf8');
     const manifest = JSON.parse(manifestString);
     const webworkersManifestString = await readFile(
       '../web/dist/webworkers/manifest.json',
       'utf8',
     );
     const webworkersManifest = JSON.parse(webworkersManifestString);
     assetInfo = {
       jsURL: `compiled/${manifest['browser.js']}`,
       fontsURL: googleFontsURL,
       cssInclude: html`
         <link
           rel="stylesheet"
           type="text/css"
           href="compiled/${manifest['browser.css']}"
         />
       `,
       olmFilename: manifest['olm.wasm'],
       commQueryExecutorFilename: webworkersManifest['comm_query_executor.wasm'],
       opaqueURL: `compiled/${manifest['comm_opaque2_wasm_bg.wasm']}`,
     };
     return assetInfo;
   } catch {
     throw new Error(
       'Could not load manifest.json for web build. ' +
         'Did you forget to run `yarn dev` in the web folder?',
     );
   }
 }
 
 let webpackCompiledRootComponent: ?React.ComponentType<{}> = null;
 async function getWebpackCompiledRootComponentForSSR() {
   if (webpackCompiledRootComponent) {
     return webpackCompiledRootComponent;
   }
   try {
     // $FlowFixMe web/dist doesn't always exist
     const webpackBuild = await import('web/dist/app.build.cjs');
     webpackCompiledRootComponent = webpackBuild.app.default;
     return webpackCompiledRootComponent;
   } catch {
     throw new Error(
       'Could not load app.build.cjs. ' +
         'Did you forget to run `yarn dev` in the web folder?',
     );
   }
 }
 
 const initialReduxStateValidator = tShape({
   navInfo: navInfoValidator,
   deviceID: t.Nil,
   currentUserInfo: currentUserInfoValidator,
   draftStore: t.irreducible('default draftStore', _isEqual({ drafts: {} })),
   sessionID: t.maybe(t.String),
   entryStore: entryStoreValidator,
   threadStore: threadStoreValidator,
   userStore: tShape({
     userInfos: userInfosValidator,
     inconsistencyReports: t.irreducible(
       'default inconsistencyReports',
       _isEqual([]),
     ),
   }),
   messageStore: messageStoreValidator,
   loadingStatuses: t.irreducible('default loadingStatuses', _isEqual({})),
   calendarFilters: t.irreducible(
     'defaultCalendarFilters',
     _isEqual(defaultCalendarFilters),
   ),
   communityPickerStore: t.irreducible(
     'default communityPickerStore',
     _isEqual({ chat: null, calendar: null }),
   ),
   windowDimensions: t.irreducible(
     'default windowDimensions',
     _isEqual({ width: 0, height: 0 }),
   ),
   notifPermissionAlertInfo: t.irreducible(
     'default notifPermissionAlertInfo',
     _isEqual(defaultNotifPermissionAlertInfo),
   ),
   connection: tShape({
     status: tString('connecting'),
     queuedActivityUpdates: t.irreducible(
       'default queuedActivityUpdates',
       _isEqual([]),
     ),
     actualizedCalendarQuery: tShape({
       startDate: t.String,
       endDate: t.String,
       filters: t.irreducible(
         'default filters',
         _isEqual(defaultCalendarFilters),
       ),
     }),
     lateResponses: t.irreducible('default lateResponses', _isEqual([])),
     showDisconnectedBar: tBool(false),
   }),
   watchedThreadIDs: t.irreducible('default watchedThreadIDs', _isEqual([])),
   lifecycleState: tString('active'),
   enabledApps: t.irreducible(
     'defaultWebEnabledApps',
     _isEqual(defaultWebEnabledApps),
   ),
   reportStore: t.irreducible(
     'default reportStore',
     _isEqual({
       enabledReports: defaultEnabledReports,
       queuedReports: [],
     }),
   ),
   nextLocalID: tNumber(0),
   deviceToken: t.Nil,
   dataLoaded: t.Boolean,
   windowActive: tBool(true),
   userPolicies: t.irreducible('default userPolicies', _isEqual({})),
   cryptoStore: t.irreducible(
     'default cryptoStore',
     _isEqual({
       primaryIdentityKeys: null,
       notificationIdentityKeys: null,
     }),
   ),
   pushApiPublicKey: t.maybe(t.String),
   _persist: t.Nil,
   commServicesAccessToken: t.Nil,
   inviteLinksStore: inviteLinksStoreValidator,
   lastCommunicatedPlatformDetails: t.irreducible(
     'default lastCommunicatedPlatformDetails',
     _isEqual({}),
   ),
   keyserverStore: keyserverStoreValidator,
 });
 
 async function websiteResponder(
   viewer: Viewer,
   req: $Request,
   res: $Response,
 ): Promise<void> {
   const appURLFacts = getAppURLFactsFromRequestURL(req.originalUrl);
   const { basePath, baseDomain } = appURLFacts;
   const baseURL = basePath.replace(/\/$/, '');
   const urlPrefix = baseDomain + baseURL;
 
   const loadingPromise = getWebpackCompiledRootComponentForSSR();
   const hasNotAcknowledgedPoliciesPromise = hasAnyNotAcknowledgedPolicies(
     viewer.id,
     baseLegalPolicies,
   );
 
   const initialNavInfoPromise = (async () => {
     try {
-      const urlInfo = infoFromURL(req.url);
+      let urlInfo = infoFromURL(decodeURI(req.url));
+
+      try {
+        urlInfo = await validateInput(viewer, urlInfoValidator, urlInfo, true);
+      } catch (exc) {
+        // We should still be able to handle older links
+        if (exc.message !== 'invalid_client_id_prefix') {
+          throw exc;
+        }
+      }
 
       let backupInfo = {
         now: currentDateInTimeZone(viewer.timeZone),
       };
       // Some user ids in selectedUserList might not exist in the userStore
       // (e.g. they were included in the results of the user search endpoint)
       // Because of that we keep their userInfos inside the navInfo.
       if (urlInfo.selectedUserList) {
         const fetchedUserInfos = await fetchUserInfos(urlInfo.selectedUserList);
         const userInfos = {};
         for (const userID in fetchedUserInfos) {
           const userInfo = fetchedUserInfos[userID];
           if (userInfo.username) {
             userInfos[userID] = userInfo;
           }
         }
         backupInfo = { userInfos, ...backupInfo };
       }
       return navInfoFromURL(urlInfo, backupInfo);
     } catch (e) {
       throw new ServerError(e.message);
     }
   })();
 
   const calendarQueryPromise = (async () => {
     const initialNavInfo = await initialNavInfoPromise;
     return {
       startDate: initialNavInfo.startDate,
       endDate: initialNavInfo.endDate,
       filters: defaultCalendarFilters,
     };
   })();
   const messageSelectionCriteria = { joinedThreads: true };
   const initialTime = Date.now();
 
   const assetInfoPromise = getAssetInfo();
   const threadInfoPromise = fetchThreadInfos(viewer);
   const messageInfoPromise = fetchMessageInfos(
     viewer,
     messageSelectionCriteria,
     defaultNumberPerThread,
   );
   const entryInfoPromise = (async () => {
     const calendarQuery = await calendarQueryPromise;
     return await fetchEntryInfos(viewer, [calendarQuery]);
   })();
   const currentUserInfoPromise = fetchCurrentUserInfo(viewer);
   const userInfoPromise = fetchKnownUserInfos(viewer);
 
   const sessionIDPromise = (async () => {
     const calendarQuery = await calendarQueryPromise;
     if (viewer.loggedIn) {
       await setNewSession(viewer, calendarQuery, initialTime);
     }
     return viewer.sessionID;
   })();
 
   const threadStorePromise = (async () => {
     const [{ threadInfos }, hasNotAcknowledgedPolicies] = await Promise.all([
       threadInfoPromise,
       hasNotAcknowledgedPoliciesPromise,
     ]);
     return { threadInfos: hasNotAcknowledgedPolicies ? {} : threadInfos };
   })();
   const messageStorePromise = (async () => {
     const [
       { threadInfos },
       { rawMessageInfos, truncationStatuses },
       hasNotAcknowledgedPolicies,
     ] = await Promise.all([
       threadInfoPromise,
       messageInfoPromise,
       hasNotAcknowledgedPoliciesPromise,
     ]);
     if (hasNotAcknowledgedPolicies) {
       return {
         messages: {},
         threads: {},
         local: {},
         currentAsOf: { [ashoatKeyserverID]: 0 },
       };
     }
     const { messageStore: freshStore } = freshMessageStore(
       rawMessageInfos,
       truncationStatuses,
       mostRecentMessageTimestamp(rawMessageInfos, initialTime),
       threadInfos,
     );
     return freshStore;
   })();
   const entryStorePromise = (async () => {
     const [{ rawEntryInfos }, hasNotAcknowledgedPolicies] = await Promise.all([
       entryInfoPromise,
       hasNotAcknowledgedPoliciesPromise,
     ]);
     if (hasNotAcknowledgedPolicies) {
       return {
         entryInfos: {},
         daysToEntries: {},
         lastUserInteractionCalendar: 0,
       };
     }
     return {
       entryInfos: _keyBy('id')(rawEntryInfos),
       daysToEntries: daysToEntriesFromEntryInfos(rawEntryInfos),
       lastUserInteractionCalendar: initialTime,
     };
   })();
   const userStorePromise = (async () => {
     const [userInfos, hasNotAcknowledgedPolicies] = await Promise.all([
       userInfoPromise,
       hasNotAcknowledgedPoliciesPromise,
     ]);
     return {
       userInfos: hasNotAcknowledgedPolicies ? {} : userInfos,
       inconsistencyReports: [],
     };
   })();
 
   const navInfoPromise = (async () => {
     const [
       { threadInfos },
       messageStore,
       currentUserInfo,
       userStore,
       finalNavInfo,
     ] = await Promise.all([
       threadInfoPromise,
       messageStorePromise,
       currentUserInfoPromise,
       userStorePromise,
       initialNavInfoPromise,
     ]);
 
     const requestedActiveChatThreadID = finalNavInfo.activeChatThreadID;
     if (
       requestedActiveChatThreadID &&
       !threadIsPending(requestedActiveChatThreadID) &&
       !threadHasPermission(
         threadInfos[requestedActiveChatThreadID],
         threadPermissions.VISIBLE,
       )
     ) {
       finalNavInfo.activeChatThreadID = null;
     }
 
     if (!finalNavInfo.activeChatThreadID) {
       const mostRecentThread = mostRecentlyReadThread(
         messageStore,
         threadInfos,
       );
       if (mostRecentThread) {
         finalNavInfo.activeChatThreadID = mostRecentThread;
       }
     }
 
     if (
       finalNavInfo.activeChatThreadID &&
       threadIsPending(finalNavInfo.activeChatThreadID) &&
       finalNavInfo.pendingThread?.id !== finalNavInfo.activeChatThreadID
     ) {
       const pendingThreadData = parsePendingThreadID(
         finalNavInfo.activeChatThreadID,
       );
       if (
         pendingThreadData &&
         pendingThreadData.threadType !== threadTypes.SIDEBAR &&
         currentUserInfo.id
       ) {
         const { userInfos } = userStore;
         const members = [...pendingThreadData.memberIDs, currentUserInfo.id]
           .map(id => {
             const userInfo = userInfos[id];
             if (!userInfo || !userInfo.username) {
               return undefined;
             }
             const { username } = userInfo;
             return { id, username };
           })
           .filter(Boolean);
         const newPendingThread = createPendingThread({
           viewerID: currentUserInfo.id,
           threadType: pendingThreadData.threadType,
           members,
         });
         finalNavInfo.activeChatThreadID = newPendingThread.id;
         finalNavInfo.pendingThread = newPendingThread;
       }
     }
 
     return finalNavInfo;
   })();
   const currentAsOfPromise = (async () => {
     const hasNotAcknowledgedPolicies = await hasNotAcknowledgedPoliciesPromise;
     return hasNotAcknowledgedPolicies ? 0 : initialTime;
   })();
 
   const pushApiPublicKeyPromise = (async () => {
     const pushConfig = await getWebPushConfig();
     if (!pushConfig) {
       if (process.env.NODE_ENV !== 'development') {
         console.warn('keyserver/secrets/web_push_config.json should exist');
       }
       return null;
     }
     return pushConfig.publicKey;
   })();
 
   const inviteLinksStorePromise = (async () => {
     const primaryInviteLinks = await fetchPrimaryInviteLinks(viewer);
     const links = {};
     for (const link of primaryInviteLinks) {
       if (link.primary) {
         links[link.communityID] = {
           primaryLink: link,
         };
       }
     }
     return {
       links,
     };
   })();
 
   const keyserverStorePromise = (async () => {
     const { sessionID, updatesCurrentAsOf } = await promiseAll({
       sessionID: sessionIDPromise,
       updatesCurrentAsOf: currentAsOfPromise,
     });
 
     return {
       keyserverInfos: {
         [ashoatKeyserverID]: {
           cookie: undefined,
           sessionID,
           updatesCurrentAsOf,
           urlPrefix,
         },
       },
     };
   })();
 
   const {
     jsURL,
     fontsURL,
     cssInclude,
     olmFilename,
     opaqueURL,
     commQueryExecutorFilename,
   } = await assetInfoPromise;
 
   // prettier-ignore
   res.write(html`
     <!DOCTYPE html>
     <html lang="en">
       <head>
         <meta charset="utf-8" />
         <title>${getTitle(0)}</title>
         <base href="${basePath}" />
         <link rel="stylesheet" type="text/css" href="${fontsURL}" />
         ${cssInclude}
         <link
           rel="apple-touch-icon"
           sizes="180x180"
           href="apple-touch-icon.png"
         />
         <link
           rel="icon"
           type="image/png"
           sizes="32x32"
           href="favicon-32x32.png"
         />
         <link
           rel="icon"
           type="image/png"
           sizes="16x16"
           href="favicon-16x16.png"
         />
         <link rel="manifest" href="site.webmanifest" />
         <meta name="apple-mobile-web-app-title" content="Comm" />
         <meta name="application-name" content="Comm" />
         <meta name="msapplication-TileColor" content="#b91d47" />
         <meta name="theme-color" content="#b91d47" />
       </head>
       <body>
         <div id="react-root">
   `);
 
   const Loading = await loadingPromise;
   const reactStream = renderToNodeStream(<Loading />);
   reactStream.pipe(res, { end: false });
 
   await waitForStream(reactStream);
   res.write(html`
     </div>
     <script>
       var preloadedState =
   `);
 
   const initialReduxState = await promiseAll({
     navInfo: navInfoPromise,
     deviceID: null,
     currentUserInfo: currentUserInfoPromise,
     draftStore: { drafts: {} },
     sessionID: sessionIDPromise,
     entryStore: entryStorePromise,
     threadStore: threadStorePromise,
     userStore: userStorePromise,
     messageStore: messageStorePromise,
     loadingStatuses: {},
     calendarFilters: defaultCalendarFilters,
     communityPickerStore: { chat: null, calendar: null },
     windowDimensions: { width: 0, height: 0 },
     notifPermissionAlertInfo: defaultNotifPermissionAlertInfo,
     connection: (async () => ({
       ...defaultConnectionInfo(viewer.platform ?? 'web', viewer.timeZone),
       actualizedCalendarQuery: await calendarQueryPromise,
     }))(),
     watchedThreadIDs: [],
     lifecycleState: 'active',
     enabledApps: defaultWebEnabledApps,
     reportStore: {
       enabledReports: defaultEnabledReports,
       queuedReports: [],
     },
     nextLocalID: 0,
     deviceToken: null,
     dataLoaded: viewer.loggedIn,
     windowActive: true,
     userPolicies: {},
     cryptoStore: {
       primaryIdentityKeys: null,
       notificationIdentityKeys: null,
     },
     pushApiPublicKey: pushApiPublicKeyPromise,
     _persist: null,
     commServicesAccessToken: null,
     inviteLinksStore: inviteLinksStorePromise,
     lastCommunicatedPlatformDetails: {},
     keyserverStore: keyserverStorePromise,
   });
   const validatedInitialReduxState = validateOutput(
     viewer.platformDetails,
     initialReduxStateValidator,
     initialReduxState,
     true,
   );
   const jsonStream = streamJSON(res, validatedInitialReduxState);
 
   await waitForStream(jsonStream);
   res.end(html`
     ;
           var baseURL = "${baseURL}";
           var olmFilename = "${olmFilename}";
           var commQueryExecutorFilename = "${commQueryExecutorFilename}";
           var opaqueURL = "${opaqueURL}";
         </script>
         <script src="${jsURL}"></script>
       </body>
     </html>
   `);
 }
 
 const inviteSecretRegex = /^[a-z0-9]+$/i;
 
 // On native, if this responder is called, it means that the app isn't
 // installed.
 async function inviteResponder(req: $Request, res: $Response): Promise<void> {
   const { secret } = req.params;
   const userAgent = req.get('User-Agent');
   const detectionResult = detectBrowser(userAgent);
   if (detectionResult.os === 'Android OS') {
     const isSecretValid = inviteSecretRegex.test(secret);
     const referrer = isSecretValid
       ? `&referrer=${encodeURIComponent(`utm_source=invite/${secret}`)}`
       : '';
     const redirectUrl = `${stores.googlePlayUrl}${referrer}`;
     res.writeHead(301, {
       Location: redirectUrl,
     });
     res.end();
     return;
   } else if (detectionResult.os !== 'iOS') {
     const urlFacts = getCommAppURLFacts();
     const baseDomain = urlFacts?.baseDomain ?? '';
     const basePath = urlFacts?.basePath ?? '/';
     const redirectUrl = `${baseDomain}${basePath}handle/invite/${secret}`;
     res.writeHead(301, {
       Location: redirectUrl,
     });
     res.end();
     return;
   }
   const fontsURL = await getFontsURL();
   res.end(html`
     <!DOCTYPE html>
     <html lang="en">
       <head>
         <meta charset="utf-8" />
         <title>Comm</title>
         <link rel="stylesheet" type="text/css" href="/${fontsURL}" />
         <style>
           * {
             -webkit-font-smoothing: antialiased;
             -moz-osx-font-smoothing: grayscale;
             box-sizing: border-box;
             padding: 0;
             margin: 0;
           }
 
           html {
             height: 100%;
             font-size: 112.5%;
           }
 
           body {
             font-family: 'Inter', -apple-system, 'Segoe UI', 'Roboto', 'Oxygen',
               'Ubuntu', 'Cantarell', 'Fira Sans', 'Droid Sans', 'Helvetica Neue',
               ui-sans-serif;
             background: #0a0a0a url('/images/invite_link_background.png')
               no-repeat;
             background-size: cover;
             color: #ffffff;
             display: flex;
             flex-direction: column;
             justify-content: space-around;
             align-items: center;
             height: 100%;
             padding: 1.6rem;
             font-size: 1.8rem;
             line-height: 2.4rem;
             font-weight: 500;
           }
 
           section {
             display: flex;
             flex-direction: column;
             align-items: center;
             justify-content: space-between;
             width: 100%;
           }
 
           .card {
             width: 100%;
             padding: 3.2rem 1.6rem;
             gap: 4rem;
             background-color: #1f1f1f;
             border-radius: 1.6rem;
           }
 
           .buttons {
             gap: 1.2rem;
           }
 
           h1 {
             font-size: 3.6rem;
             line-height: 1.5;
             font-weight: 500;
             font-family: 'IBM Plex Sans', sans-serif;
           }
 
           p {
             text-align: center;
           }
 
           .separator {
             border: 1px solid #404040;
             width: 100%;
           }
 
           .button {
             all: unset;
             box-sizing: border-box;
             display: flex;
             justify-content: center;
             align-items: center;
             width: 100%;
             padding: 1.7rem;
             border-radius: 0.4rem;
             border: 1px solid transparent;
             background-color: #6d49ab;
             font-size: 1.6rem;
             line-height: 1.5;
           }
 
           .button.secondary {
             background-color: #1f1f1f;
             border-color: #ffffff;
           }
 
           .link {
             all: unset;
             box-sizing: border-box;
             display: flex;
             align-items: center;
           }
 
           .link-text {
             text-decoration-line: underline;
           }
 
           .logo-container {
             background-color: #0a0a0a;
             width: 4.2rem;
             height: 4.2rem;
             display: flex;
             justify-content: center;
             align-items: center;
             border-radius: 50%;
           }
 
           .logo {
             height: 2.6rem;
           }
 
           .arrow {
             width: 1.8rem;
             height: 1.8rem;
           }
         </style>
       </head>
       <body>
         <div></div>
         <section class="card">
           <section>
             <div class="logo-container">
               <img
                 src="/images/loading_logo.svg"
                 alt="Comm logo"
                 class="logo"
               />
             </div>
             <h1>Comm</h1>
           </section>
           <p>
             To join this community, download the Comm app and reopen this invite
             link
           </p>
           <div class="separator"></div>
           <section class="buttons">
             <a class="button" href="${stores.appStoreUrl}">Download Comm</a>
             <a class="button secondary" href="${inviteLinkUrl(secret)}">
               Invite Link
             </a>
           </section>
         </section>
         <a class="link" href="https://comm.app/">
           <span class="link-text">Visit Comm’s website</span>
           <img
             src="/images/arrow_up_right.svg"
             alt="arrow up right"
             class="arrow"
           />
         </a>
       </body>
     </html>
   `);
 }
 
 export { websiteResponder, inviteResponder };
diff --git a/keyserver/src/utils/validation-utils.js b/keyserver/src/utils/validation-utils.js
index 7844d75d1..354febd5b 100644
--- a/keyserver/src/utils/validation-utils.js
+++ b/keyserver/src/utils/validation-utils.js
@@ -1,237 +1,239 @@
 // @flow
 
 import type { TType } from 'tcomb';
 
 import type { PolicyType } from 'lib/facts/policies.js';
 import {
   hasMinCodeVersion,
   hasMinStateVersion,
 } from 'lib/shared/version-utils.js';
 import { type PlatformDetails } from 'lib/types/device-types.js';
 import {
   convertClientIDsToServerIDs,
   convertObject,
   convertServerIDsToClientIDs,
 } from 'lib/utils/conversion-utils.js';
 import { ServerError } from 'lib/utils/errors.js';
 import {
   tCookie,
   tPassword,
   tPlatform,
   tPlatformDetails,
   assertWithValidator,
   ashoatKeyserverID,
 } from 'lib/utils/validation-utils.js';
 
 import { fetchNotAcknowledgedPolicies } from '../fetchers/policy-acknowledgment-fetchers.js';
 import { verifyClientSupported } from '../session/version.js';
 import type { Viewer } from '../session/viewer.js';
 
 async function validateInput<T>(
   viewer: Viewer,
   inputValidator: TType<T>,
   input: mixed,
+  ignoreViewerVersion?: boolean,
 ): Promise<T> {
-  if (!viewer.isSocket) {
+  if (!ignoreViewerVersion && !viewer.isSocket) {
     await checkClientSupported(viewer, inputValidator, input);
   }
   const convertedInput = checkInputValidator(inputValidator, input);
 
   if (
     hasMinStateVersion(viewer.platformDetails, {
       native: 43,
       web: 3,
-    })
+    }) ||
+    ignoreViewerVersion
   ) {
     try {
       return convertClientIDsToServerIDs(
         ashoatKeyserverID,
         inputValidator,
         convertedInput,
       );
     } catch (err) {
       throw new ServerError(err.message);
     }
   }
 
   return convertedInput;
 }
 
 function validateOutput<T>(
   platformDetails: ?PlatformDetails,
   outputValidator: TType<T>,
   data: T,
   alwaysConvertSchema?: boolean,
 ): T {
   if (!outputValidator.is(data)) {
     console.trace(
       'Output validation failed, validator is:',
       outputValidator.displayName,
     );
     return data;
   }
 
   if (
     hasMinStateVersion(platformDetails, {
       native: 43,
       web: 3,
     }) ||
     alwaysConvertSchema
   ) {
     return convertServerIDsToClientIDs(
       ashoatKeyserverID,
       outputValidator,
       data,
     );
   }
 
   return data;
 }
 
 function checkInputValidator<T>(inputValidator: TType<T>, input: mixed): T {
   if (inputValidator.is(input)) {
     return assertWithValidator(input, inputValidator);
   }
   const error = new ServerError('invalid_parameters');
   error.sanitizedInput = input ? sanitizeInput(inputValidator, input) : null;
   throw error;
 }
 
 async function checkClientSupported<T>(
   viewer: Viewer,
   inputValidator: ?TType<T>,
   input: T,
 ) {
   let platformDetails;
   if (inputValidator) {
     platformDetails = findFirstInputMatchingValidator(
       inputValidator,
       tPlatformDetails,
       input,
     );
   }
   if (!platformDetails && inputValidator) {
     const platform = findFirstInputMatchingValidator(
       inputValidator,
       tPlatform,
       input,
     );
     if (platform) {
       platformDetails = { platform };
     }
   }
   if (!platformDetails) {
     ({ platformDetails } = viewer);
   }
   await verifyClientSupported(viewer, platformDetails);
 }
 
 const redactedString = '********';
 const redactedTypes = [tPassword, tCookie];
 function sanitizeInput<T>(inputValidator: TType<T>, input: T): T {
   return convertObject(
     inputValidator,
     input,
     redactedTypes,
     () => redactedString,
   );
 }
 
 function findFirstInputMatchingValidator(
   wholeInputValidator: *,
   inputValidatorToMatch: *,
   input: *,
 ): any {
   if (!wholeInputValidator || input === null || input === undefined) {
     return null;
   }
   if (
     wholeInputValidator === inputValidatorToMatch &&
     wholeInputValidator.is(input)
   ) {
     return input;
   }
   if (wholeInputValidator.meta.kind === 'maybe') {
     return findFirstInputMatchingValidator(
       wholeInputValidator.meta.type,
       inputValidatorToMatch,
       input,
     );
   }
   if (
     wholeInputValidator.meta.kind === 'interface' &&
     typeof input === 'object'
   ) {
     for (const key in input) {
       const value = input[key];
       const validator = wholeInputValidator.meta.props[key];
       const innerResult = findFirstInputMatchingValidator(
         validator,
         inputValidatorToMatch,
         value,
       );
       if (innerResult) {
         return innerResult;
       }
     }
   }
   if (wholeInputValidator.meta.kind === 'union') {
     for (const validator of wholeInputValidator.meta.types) {
       if (validator.is(input)) {
         return findFirstInputMatchingValidator(
           validator,
           inputValidatorToMatch,
           input,
         );
       }
     }
   }
   if (wholeInputValidator.meta.kind === 'list' && Array.isArray(input)) {
     const validator = wholeInputValidator.meta.type;
     for (const value of input) {
       const innerResult = findFirstInputMatchingValidator(
         validator,
         inputValidatorToMatch,
         value,
       );
       if (innerResult) {
         return innerResult;
       }
     }
   }
   return null;
 }
 
 async function policiesValidator(
   viewer: Viewer,
   policies: $ReadOnlyArray<PolicyType>,
 ) {
   if (!policies.length) {
     return;
   }
   if (!hasMinCodeVersion(viewer.platformDetails, { native: 181 })) {
     return;
   }
 
   const notAcknowledgedPolicies = await fetchNotAcknowledgedPolicies(
     viewer.id,
     policies,
   );
 
   if (notAcknowledgedPolicies.length) {
     throw new ServerError('policies_not_accepted', {
       notAcknowledgedPolicies,
     });
   }
 }
 
 export {
   validateInput,
   validateOutput,
   checkInputValidator,
   redactedString,
   sanitizeInput,
   findFirstInputMatchingValidator,
   checkClientSupported,
   policiesValidator,
 };
diff --git a/lib/utils/url-utils.js b/lib/utils/url-utils.js
index dd97b7cc6..8914404cc 100644
--- a/lib/utils/url-utils.js
+++ b/lib/utils/url-utils.js
@@ -1,102 +1,118 @@
 // @flow
 
-import { idSchemaRegex } from './validation-utils.js';
+import t, { type TInterface } from 'tcomb';
+
+import { idSchemaRegex, tID, tShape } from './validation-utils.js';
 import { pendingThreadIDRegex } from '../shared/thread-utils.js';
 
 export type URLInfo = {
   +year?: number,
   +month?: number, // 1-indexed
   +verify?: string,
   +calendar?: boolean,
   +chat?: boolean,
   +thread?: string,
   +settings?: 'account' | 'danger-zone',
   +threadCreation?: boolean,
   +selectedUserList?: $ReadOnlyArray<string>,
   +inviteSecret?: string,
   +qrCode?: boolean,
   ...
 };
 
+export const urlInfoValidator: TInterface<URLInfo> = tShape<URLInfo>({
+  year: t.maybe(t.Number),
+  month: t.maybe(t.Number),
+  verify: t.maybe(t.String),
+  calendar: t.maybe(t.Boolean),
+  chat: t.maybe(t.Boolean),
+  thread: t.maybe(tID),
+  settings: t.maybe(t.enums.of(['account', 'danger-zone'])),
+  threadCreation: t.maybe(t.Boolean),
+  selectedUserList: t.maybe(t.list(t.String)),
+  inviteSecret: t.maybe(t.String),
+  qrCode: t.maybe(t.Boolean),
+});
+
 // We use groups to capture parts of the URL and any changes
 // to regexes must be reflected in infoFromURL.
 const yearRegex = new RegExp('(/|^)year/([0-9]+)(/|$)', 'i');
 const monthRegex = new RegExp('(/|^)month/([0-9]+)(/|$)', 'i');
 const threadRegex = new RegExp(`(/|^)thread/(${idSchemaRegex})(/|$)`, 'i');
 const verifyRegex = new RegExp('(/|^)verify/([a-f0-9]+)(/|$)', 'i');
 const calendarRegex = new RegExp('(/|^)calendar(/|$)', 'i');
 const chatRegex = new RegExp('(/|^)chat(/|$)', 'i');
 const accountSettingsRegex = new RegExp('(/|^)settings/account(/|$)', 'i');
 const dangerZoneRegex = new RegExp('(/|^)settings/danger-zone(/|$)', 'i');
 const threadPendingRegex = new RegExp(
   `(/|^)thread/(${pendingThreadIDRegex})(/|$)`,
   'i',
 );
 const threadCreationRegex = new RegExp(
   '(/|^)thread/new(/([0-9]+([+][0-9]+)*))?(/|$)',
   'i',
 );
 const inviteLinkRegex = new RegExp(
   '(/|^)handle/invite/([a-zA-Z0-9]+)(/|$)',
   'i',
 );
 const qrCodeLoginRegex = new RegExp('(/|^)qr-code(/|$)', 'i');
 
 function infoFromURL(url: string): URLInfo {
   const yearMatches = yearRegex.exec(url);
   const monthMatches = monthRegex.exec(url);
   const threadMatches = threadRegex.exec(url);
   const verifyMatches = verifyRegex.exec(url);
   const calendarTest = calendarRegex.test(url);
   const chatTest = chatRegex.test(url);
   const accountSettingsTest = accountSettingsRegex.test(url);
   const dangerZoneTest = dangerZoneRegex.test(url);
   const threadPendingMatches = threadPendingRegex.exec(url);
   const threadCreateMatches = threadCreationRegex.exec(url);
   const inviteLinkMatches = inviteLinkRegex.exec(url);
   const qrCodeLoginMatches = qrCodeLoginRegex.exec(url);
 
   const returnObj = {};
   if (yearMatches) {
     returnObj.year = parseInt(yearMatches[2], 10);
   }
   if (monthMatches) {
     const month = parseInt(monthMatches[2], 10);
     if (month < 1 || month > 12) {
       throw new Error('invalid_month');
     }
     returnObj.month = month;
   }
   if (threadMatches) {
     returnObj.thread = threadMatches[2];
   }
   if (threadPendingMatches) {
     returnObj.thread = threadPendingMatches[2];
   }
   if (threadCreateMatches) {
     returnObj.threadCreation = true;
     returnObj.selectedUserList = threadCreateMatches[3]?.split('+') ?? [];
   }
   if (verifyMatches) {
     returnObj.verify = verifyMatches[2];
   }
   if (inviteLinkMatches) {
     returnObj.inviteSecret = inviteLinkMatches[2];
   }
   if (calendarTest) {
     returnObj.calendar = true;
   } else if (chatTest) {
     returnObj.chat = true;
   } else if (accountSettingsTest) {
     returnObj.settings = 'account';
   } else if (dangerZoneTest) {
     returnObj.settings = 'danger-zone';
   } else if (qrCodeLoginMatches) {
     returnObj.qrCode = true;
   }
   return returnObj;
 }
 
 const setURLPrefix = 'SET_URL_PREFIX';
 
 export { infoFromURL, setURLPrefix };