Mozilla further warned that a working exploit has been publically released, increasing the risk of attacks occurring in the wild.
Users can also reduce the risk of attack by running the browser in Windows Safe Mode.
The flaw is the latest in a string of high-profile browser exploits in recent days. Last week Microsoft warned of a flaw in a video ActiveX plug-in that was actively being targeted in Internet Explorer, and yesterday the company reported a second vulnerable IE component, this time an Office plug-in, that was being targeted by attackers.
IBM and Technical University of Munich team demonstrate how Shor's algorithm, which can't be cracked by conventional computers, can be solved quickly with quantum computing
Hubble Space Telescope finds superflares from young red dwarfs could strip away planetary atmosphere
Younger stars are 100 to 1,000 times more energetic than when they're older
Two of the big four supermarkets will use the system to control sales of restricted products
PUBG news and updates: November's Update #23 to bring new Skorpion pistol and changes to blue zone visibility
Genuinely useful side-arm coming to PUBG in Update #23