nah, that is overkill. the probability of falling for this is still tiny and it cannot break the sandbox, steal session cookies, or anything like that .
Sandbox escapes are discovered all the time (pretty sure I've read about a few just this past week) and there are a lot of other problems CSS can enable (ads, fingerprinting, etc)
Sandbox escapes are discovered all the time (pretty sure I've read about a few just this past week) and there are a lot of other problems CSS can enable (ads, fingerprinting, etc)