Firefox user Sijie Xia reported that if a user explicitly removes the trust for extended validation (EV) capable root certificates in the certificate manager, the change is not properly used when validating EV certificates, causing the setting to be ignored. This removes the ability of users to explicitly untrust root certificates from specific certificate authorities.

This flaw does not affect certificates that are not extended validation certificates. All other certificate validation checks do occur, the error is the assumption that if Mozilla trusted the certificate, the user would also.


External Reference:

http://www.mozilla.org/security/announce/2013/mfsa2013-113.html


Acknowledgements:

Red Hat would like to thank the Mozilla project for reporting this issue. Upstream acknowledges Sijie Xia as the original reporter.