[nish__]

No. What would be the point of that?

[ceteia]

Not Firefox, but Servo has quite a lot of unsafe, even though some of the results are false positives.

https://grep.app/search?f.repo=servo%2Fservo&f.repo.pattern=...

So Servo at the very least cannot be said to be 'safe'. And I believe the Rust code in Firefox is similar.