Mozilla has rolled out a new version of its Firefox browser, an update that includes patches for four critical security vulnerabilities and several less-severe bugs. The most dangerous vulnerabilities, however, include a pair of use-after-free bugs in one part of the browser and another in a separate component, as well as a number of memory corruption flaws. In all, Firefox 39 patches 13 vulnerabilities, including two high-risk bugs and six moderate-level ones. The bugs also include a potpourri of bugs a researcher discovered through code inspection.
Source: https://threatpost.com/firefox-39-out-with-patches-for-four-critical-vulnerabilities/113686/