Messages that cannot be loaded can obfuscate attribution due to UI error

[eblanton]

Steps to reproduce

In Element Desktop in a private room, a discord bridge sent an m.sticker message that Element did not understand (which is fine), but it caused a visual display bug which mis-attributed a message. Here is an image of the misattribution, followed by a quote block containing the text from the image:

elb (neither the stickers nor the custom reacts seem to port to the Matrix side)
   Can't load this message (m.sticker) Submit debug logs
I refrained from uploading any more, since this serves as a proof of concept more than enough

The error here is that the sticker and the following message ("I refrained ...") were NOT sent by the user elb, although this is what the display implies. It seems that, because the sticker could not be shown, it does not show an attribution in the window, but because the following message was from the same sender, it also does not show an attribution.

Outcome

What did you expect?

The sticker message, or message following, would have a user attribution showing who sent those two messages.

What happened instead?

Two messages are visually attributed to a user who did not send them.

Operating system

Debian Linux

Application version

Element version: 1.11.89 Crypto version: Rust SDK 0.7.2 (2f872cf), Vodozemac 0.8.1

How did you install the app?

flatpack

Homeserver

matrix.org

Will you send logs?

No

[eblanton]

I disagree with the AI-applied minor label to this bug; a malicious user could intentionally send a message that Element believes it should show to a room, followed by an embarrassing or compromising message, and thereby cause many users to believe that the previous sender sent the problematic message.