It sounds like this happens if NSS hits shutdown before nsUrlClassifierDBService (anti-phishing thread). During xpcom-shutdown, nsUrlClassifierDBService processes pending events, which may include using nsCryptoHash.
I think the fix is to turn all pending events into NOOPs during nsUrlClassifierDBService shutdown. I'll see if I can repro and get a patch.
It sounds like this happens if NSS hits shutdown before nsUrlClassifier DBService (anti-phishing thread). During xpcom-shutdown, nsUrlClassifier DBService processes pending events, which may include using nsCryptoHash.
I think the fix is to turn all pending events into NOOPs during nsUrlClassifier DBService shutdown. I'll see if I can repro and get a patch.