Found in

• Issue caused after fixing bug 1799823. See bug 1799823 comment 17

Affected versions

• Firefox 108.0
• Latest Nightly 109.0a1

Tested platforms

• Affected platforms: Windows 10.
• Unaffected platforms: macOS, Ubuntu 22.04

Steps to reproduce:

1. Open Task Manager
2. Create a new profile
3. Add the user.js attached to the profile
4. Open Firefox
5. Exit firefox in ~2sec after it started
6. Take a look in the Task Manager

Expected result

• Firefox process quits without issues.

Actual result

• The firefox process is still opened inside Task Manager and increasing the memory until it crashes.

Additional notes

• Ever since a fix landed in bug 1799823 I can still reproduce this shutdown crash with multiple and different @shutdownhang signature
• I made a screenshare of the steps but the file is too large to upload here directly so I uploaded it to Gdrive: https://drive.google.com/file/d/1U2dEMZVQ_f2B2irypm_yTt68KU8KqSbt/view?usp=share_link
• I had multiple crashes signature, they can be seen in bug 1799823 comment 17 as well:
  108.0b9 - https://crash-stats.mozilla.org/report/index/fa4d11e1-d4f8-4580-a979-559f40221205 - [@ shutdownhang | NtUserPostMessage | PostMessageW ]
  108.0 rc - https://crash-stats.mozilla.org/report/index/71fc0d73-e810-4f5b-b58e-9c3820221209 - [@ shutdownhang | NtUserPeekMessage | _PeekMessage ]
  Latest Nightly 109.0a1 - https://crash-stats.mozilla.org/report/index/35b45c87-7c55-4ff9-8d8b-37eed0221205 - [@ shutdownhang | RtlEnterCriticalSection | Mutex::Lock ] / https://crash-stats.mozilla.org/report/index/02e6e442-1bf3-40a3-b1f6-84de80221205 - [@ shutdownhang | RtlQueryPerformanceCounter | mozilla::PerformanceCounter ]
• I am going to set this as Severity S3 since I can get those crashes only by using this particular steps with adding prefs for Remote Settings and I am not sure how big of an impact this can have on other users, please change it to S2 is need be. Also please change the component if this is not the correct one.

I can't seem to reproduce this on the latest Nightly 118.

The user.js wasn't attached, so I recreated it from the video:

user_pref("security.content.signature.root_hash", "3C:01:44:6A:BE:90:36:CE:A9:A0:9A:CA:A3:A5:20:AC:62:8F:20:A7:AE:32:CE:86:1C:B2:EF:B7:0F:A0:C7:45");
user_pref("services.settings.server", "https://settings-cdn.stage.mozaws.net/v1");

I'm pretty sure the root_hash pref no longer does anything so the only pref of note is the services.settings.server pref.
The pref definitely took effect because I immediately saw a heartbeat message that is deployed to stage (heartbeat-test)