Weird issue where entire Firefox window flashes grey with a blue box on it
It seems to be related to video playback but not sure. It was happening while a video was playing full screen, and also after stopping playing/hiding a non-full-screen video.
To catch the issue had to screen record at 240fps. I used Nvidia Overlay to record the issue, but was happening before the overlay was even enabled.
Disabled all addons, made no difference. HW acceleration on or off, still happened.
I tried turning on logs, and this always seemed to show up with the flash:
```
2026-08-09 06:19:44.048000 UTC - [Parent 8388: Main Thread]: D/Widget GetWorkspaceId - calling AsyncUpdateWorkspaceID()
2026-08-09 06:19:44.048000 UTC - [Parent 8388: BackgroundThreadPool #276]: D/Widget calling GetWindowDesktopId
2026-08-09 06:19:44.048000 UTC - [Parent 8388: Main Thread]: D/Widget GetWorkspaceId - calling AsyncUpdateWorkspaceID()
2026-08-09 06:19:44.048000 UTC - [Parent 8388: Main Thread]: D/Widget GetWorkspaceId - calling AsyncUpdateWorkspaceID()
2026-08-09 06:19:44.048000 UTC - [Parent 8388: BackgroundThreadPool #276]: D/Widget called GetWindowDesktopId, hr=00000000
2026-08-09 06:19:44.048000 UTC - [Parent 8388: BackgroundThreadPool #276]: D/Widget calling GetWindowDesktopId
2026-08-09 06:19:44.048000 UTC - [Parent 8388: BackgroundThreadPool #276]: D/Widget called GetWindowDesktopId, hr=00000000
2026-08-09 06:19:44.048000 UTC - [Parent 8388: BackgroundThreadPool #276]: D/Widget calling GetWindowDesktopId
2026-08-09 06:19:44.048000 UTC - [Parent 8388: BackgroundThreadPool #276]: D/Widget called GetWindowDesktopId, hr=00000000
```
Wšykne wótegrona (2)
Hi
Thank you for helping to test the next version of Firefox, we really appreciate it.
Does that same thing happen in the current Release version of Firefox?
Hi, yes it happens on a fresh install of Firefox 153 in a new profile. It also happened when 153 was in beta.
Musyśo se pla swójogo konta pśizjawiś, aby na pśinoski wótegronił. Pšosym stajśo pšašanje, jolic hyšći njamaśo wužywaŕske konto.