Hashes are generally a part of the signature generation used with certificates. See for example "What role do hashes play in TLS/SSL certificate validation?" -> https://security.stackexchange.com/questions/67512/what-role...

In certificates, md5 - and sha1 - was used quite some time after it was known to be weak, I suspect OP was thinking of that.

This article seems to give a good summary what happened with sha1, mentions md5 in passing and links the related chromium issue: https://konklone.com/post/why-google-is-hurrying-the-web-to-...