Except in this case, seeing as it seems that Mint hasn't got new ssl certs or private keys, the only way to 'act accordingly' is to never use the service again.
Or they were never vulnerable, which is likely given what has been dug up about their tech stack.
ah, right. i didn't consider that their private key could have been leaked if they were once vulnerable (i was only considering passwords and the like). good point, thanks!