Firefox includes a new enhancement to private browsing that allows you to open a new private browsing window without closing or changing your current browsing session.
Fixed flaws include:
MFSA 2013-40: Out-of-bounds array read in CERT_DecodeCertPackage.
MFSA 2013-39: Memory corruption while rendering grayscale PNG images.
MFSA 2013-38: Cross-site scripting (XSS) using timed history navigations.
MFSA 2013-37: Bypass of tab-modal dialog origin disclosure.
MFSA 2013-36: Bypass of SOW protections allows cloning of protected nodes.
MFSA 2013-35: WebGL crash with Mesa graphics driver on Linux.
MFSA 2013-34: Privilege escalation through Mozilla Updater.
MFSA 2013-33: World read and write access to app_tmp directory on Android.
MFSA 2013-32: Privilege escalation through Mozilla Maintenance Service.
MFSA 2013-31: Out-of-bounds write in Cairo library.
MFSA 2013-30: Miscellaneous memory safety hazards (rv:20.0 / rv:17.0.5).