Window Snyder, Mozilla's chief of security, confirmed a data leak vulnerability in Firefox's directory traversal mechanism. The flaw has been graded as low risk and was brought to light as a proof of concept.
The bug was traced the way escape sequences are handled, leading to file access on a user's PC, even though the browser is fully patched.
Firefox leaks information (Heise Security)
Mozilla Says Flaw Could Lead to Data Leak (PC World)
Mozilla says that flaw could lead to data leak (Washington Post)