Entered an encrypted media chat and selected a photo to send. Observed the Dev Tools Network tab to see that the encrypted media was preloaded:
{F567178}
Note the two subsequent requests to `b281...3d58`. The first one is sent from the preload function (`media-utils.js`, 251ms), while the other is read from `disk-cache`. Remember to uncheck the "Disable cache" option in devtools.