Mozilla has released Firefox 10.0.2, as a quick update to the recent major update. According to Mozilla Security Blog, a vulnerability was discovered in libpng, the official reference PNG library used by Firefox, Thunderbird, and plenty of other software titles, which could allow a maliciously crafted image to run arbitrary code in a user’s machine.
If you have already received the update ensure to restart as soon as possible to have the change in place. If not, in the Firefox button, select About Firefox in the Help menu to check and update if necessary.