In firefox sessions without a tor proxy, it seems worthwhile to use an extension that helps to validate SSL certificates (e.g. Perspectives or Certificate Patrol). Is there any way to handle this problem with the Tor Browser Bundle?
You can check manually, not as easy as a plugin/extension but...
Steve Gibson makes some handy tools for security, like this section- https://www.grc.com/fingerprints.htm
Simply comparing a fingerprint from his server and your browser as being identical OR not, as he explains how, will validate if the CA is being spoofed and/or intercepted pretty quick.