This issue only needs to be tested in 1 device. We'll only test the fix in messaging because the code is the same in all the places that were fixed and it requires a bunch of time to test them all. In the app, open a message discussion in online. Send the following message: <img src="x" onerror="alert(1)">. Check that you don't see any popup with the number "1". Go offline and send the message again. Check that you don't see any popup with the number "1". Optional: if you want to test any of the other features mentioned in the comments feel free to do so, but I already tested them. To do so, you'll need to generate data in offline and check that the popup isn't seen.