Found in

• Firefox 105.0b8

Affected versions

• Firefox 104.0.2
• Firefox 105.0b8
• Firefox 106.0a1
• Firefox 105.0

Tested platforms

• Affected platforms: Windows 10 x64, Windows 8.1 x64 , Ubuntu 22 x64
• Unaffected platforms: macOS 10.15

Steps to reproduce

1. Open Firefox and in about:config set: extensions.webcompat.enable_shims to true
2. Enable “Strict” Tracking protection via about:preferences#privacy
3. Go to https://www.patreon.com/login or https://www.dailymotion.com/signin
4. Interact with the website by clicking on a third-party Facebook login button
5. Observe the Facebook - Mozilla Firefox page which just appears.

Expected result

• The Facebook - Mozilla Firefox page appears correctly without shaking.

Actual Result

• The Facebook - Mozilla Firefox page shakes.

Regression range

• I will come back with regression range ASAP.

Note

• The first two steps not necessary, only open Firefox with a new profile.

Regression range
This issue is not a regression as it is reproducible on builds back to Firefox 57.0a1 (2017-09-06), reproduced partially on Ubuntu 22 x64 using Fx 105.0b9, but here the issue it's not that annoying.

This is probably just caused by the SmartBlock shim (which helps Facebook logins work in private browsing and strict ETP) not being perfect. I will investigate it ASAP, thanks for the report!