Create a new site (we need it fresh to guarantee the user's personal messaging space is in the vanilla state) Log in as the admin Enable the 'trusttext' admin setting Enable the 'messagingallusers' admin setting (site wide messaging) Enrol 7 students in a course. Now, via the messaging pane, search for each student and send the following messages, one to each student (just copy and paste the HTML into the 'write a message' text entry field): Image: <img src="https://image.shutterstock.com/image-vector/black-cat-silhouette-elegant-sitting-260nw-735404302.jpg" alt="small cat icon"> Video: <video src="https://mdn.github.io/learning-area/html/multimedia-and-embedding/video-and-audio-content/rabbit320.webm" controls> <p>Your browser doesn't support HTML5 video. Here is a <a href="rabbit320.webm">link to the video</a> instead.</p> </video> Audio: <audio controls src="https://interactive-examples.mdn.mozilla.net/media/examples/t-rex-roar.mp3"><p>Your browser doesn't support HTML5 aduio. Here is a <a href="rabbit320.webm">link to the video</a> instead.</p> </audio> Iframe content (Fallback case): <iframe id="inlineFrameExample" title="Inline Frame Example" src="https://www.openstreetmap.org/export/embed.html?bbox=-0.004017949104309083%2C51.47612752641776%2C0.00030577182769775396%2C51.478569861898606&amp;layer=mapnik" width="300" height="200"></iframe> Other media (fallback case): <embed src="https://html.com/wp-content/uploads/flamingo.jpg></embed> Texty 1: This is just a normal message Texty 2 (formatted) <span style="font-weight:bold">This message is bold</span> Now, open dev tools in your browser and reload the page. Open the messaging pane, and expand the private conversations tab (if not already done) Verify the following : All conversations are present in the section and no errors appear in the dev tools console. You see one conversation with a "<ICON> Image" description You see one conversation with a "<ICON> Video" description You see one conversation with a "<ICON> Audio" description You see two conversations with a "<ICON> Other media" description You see one conversation with "This is just a normal message" description You see one conversation with "This message is bold" description, but the message is NOT bold. Click on each of the two conversations described as having 'other media'. Verify : One is the iframe containing a map One is a picture of a flamingo (it used the embed tag, so wasn't detected as an image - this is expected). Now expand the Starred section Verify : The personal space (conversation with yourself) is present and that no js errors appear in the console. There is no description present in the personal space conversation (there is no message there yet). Now, via site admin, disable the 'trusttext' setting and save. Open messaging Expand the private messages section and Verify the same results as above - i.e. all descriptions and icons are the same and no js console errors. Click on each of the two conversations described as having 'other media'. Verify : Both contain an empty message box. Now, in your editor, open the theme/boost/config.php file. Comment out the last line, making it: //$THEME->iconsystem = \core\output\icon_system::FONTAWESOME; Purge caches Reload the page Open messaging and view the private conversations section. Verify you see the fallback icons for all 4 of the content types -image, video, audio, and other media.