Regression in current stable (version 121.0.6167.139.1) makes pages to crash on certain actions [BUG]

[ggrocca]

Describe the bug
When clicking a button on certain pages, an entire subframe or tab crashes. This does not happen on any button - just some, but those that do, they always crash. I think the crash depends on which javascript code or general action is associated to the button callback. I've noticed it immediately after install in two situations: in disqus subframes, and in an intranet app in my office. I bet this happens in several other situations, but at that point I didn't try anything else and I've just installed the previous stable.

To Reproduce
Steps to reproduce the behavior:

1. Go to any page that loads disqus comments, for example here
2. Login to disqus.
3. Write and publish any comment, for example test test test.
4. After having published the comment, click on the "modify" button under it.
5. See the whole disqus subframe crash.

Expected behavior
No frames or tabs crashing.

Screenshots
Didn't make one but I can provide one if it can be useful

Desktop (please complete the following information):

• macOS X Mojave
• Build 121.0.6167.139.1

Additional Info
This happens on the latest stable only. I've tested both versions 1257388 (123.0.6288.0, current latest) and 120.0.6099.199.1 (previous stable) and they work correctly.

[Wowfunhappy]

I can confirm this is occurring on 10.9.5 in the test case with Disqus comments.

[Wowfunhappy]

Oh yay, this generates a crash report. Looks like it's something related to focus rings? (I've attached two reports for good measure, but they're perfectly consistent.)
Archive.zip

[Wowfunhappy]

This appears to have been fixed as of 121.0.6167.160.1! This issue can be closed.