Mozilla is aware of the claim of a zero-day in Firefox as posted here: http://secunia.com/advisories/38608/. We cannot confirm the report as we have received no details regarding the reported vulnerability, such as a proof-of-concept or steps to reproduce. We’ve attempted to contact the researcher who discovered the issue but have not received a response.
Mozilla takes all reports of security vulnerabilities seriously. As always, if you have information about security issues, please send details to firstname.lastname@example.org.
Lucas Adamski, Mozilla Security