Retesting this today, I'm unable to reproduce on either of the mentioned sites here (x.com, youtube.com). --> WORKSFORME, but we can reopen if we manage to find a way to repro.
Bug 2062388 Comment 4 Edit History
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Retesting this today, I'm unable to reproduce on either of the mentioned sites here (x.com, youtube.com). Maybe my phone or Firefox instance had just gotten itself into a weird state when I triggered this? Or maybe we had a selection bug in one or two Nightlies that was later fixed? Anyway, in the absence of an ability to further investigate... --> WORKSFORME, but we can reopen if we manage to find a way to repro.