There was a hash collision bug in the main Lean kernel that was patched, but AFAIK nothing relied on it. You'd have to know what you were doing to accidentally get there...
replyThe incident in the links I posted exploited several bugs AFAICS, so it's a different story than a single hash collision bug, it seems.
replyI don't know ... do you have a reference?
replyYup, found it:
replyCool, thanks!
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