For regular bugs, please report them in our issue tracker.
If you believe that you've found a security vulnerability, please file a secure bug report in our bug tracker or send an email to security AT mozilla DOT org.
For more information on security-related bug disclosure and the PGP key to use for sending encrypted mail or to verify responses received from that address, please read our wiki page at https://www.mozilla.org/en-US/security/#For_Developers.