#734 Opening some messages causes flashing screen, intermittent crash

[tlhackque]

Some messages, when opened with Enigmail enabled, cause the message to flash continuously. I've only seen it on digest format mailing list messages; it seems to happen when some users post.

The screen turns white, one sees the message paint, then it flashes white. This continues at a high rate.

This happens when opening in a new pane - but also in the preview pane.

While this is going on, the status bar reads "loading message" - flashing with the rest of the screen.

There seems to be some resource depletion; if I let the flashing continue for some time, Thunderbird frequently crashes or hangs thereafter.

In the attached example:
Loaded as a standalone message, it does NOT flash, but reports "5 attachments, 19.2KB"
While read from my (IMAP) inbox, it DOES flash, but reports 6 attachments.

The attachment count doesn't flash.

This was the last message in my inbox (/var/spool/mail/username). The behavior persists when additional mail is delivered.

There may be other preconditions for getting this to reproduce.

**If I disable Enigmail, these messages open correctly. Re-enabling causes the symptom to recurr.
**

One crash (folllowing a different message that flashes) is Mozilla crash ID Crash ID: bp-15194888-293f-4b5b-98ee-e2a670180123
The dump can be found at https://crash-stats.mozilla.com/report/index/15194888-293f-4b5b-98ee-e2a670180123

Thunderbird 52.5.2 (32-bit).

The inbox file is ~81M.

I marked this as "private" because if someone can figure out how to craft an e-mail with these symptoms, it seems as though Thunderbird goes out of control. However, there is no evidence of permanent harm. Continuous flashing based on a received message seems to me to be a way to attack a recipient's UI. It can be difficult to get it to stop. I suppose it might also be an issue for triggering epileptic seizures in those sensitive to flashing. In a sense, this is denial of service; it certainly corrupts the UI.

Note: This was initially reported as Thunderbird bug https://bugzilla.mozilla.org/show_bug.cgi?id=1432218 (marked private)

[tlhackque]

I was able to capture a short video that demonstrates the effect. The video capture software seems to sample the screen asynchronously, so it seems slower in the video than in real life and some of the text seems faint . These are artifacts of the screen capture.

The screen capture area didn't include the "loading message" status.

But you can see the screen flashing and the attachment count cycling between 6 and 10.

All I did to invoke this was to double-click on the message.

Note that this is a different message. I don't seem to be able to attach 2 files to this update, so the message is here, the next reply will have the video.

[tlhackque]

Here is the video.

[Patrick Brunschwig]

That's already fixed on Enigmail master (v2.0)