I received this email and thought that I should share this.
For all firefox users, it is recommended that you switch to an alternate browser till a patch is made available.
According to this article in ARSTechnica
"There's a zero-day exploit in the wild that's being used to execute malicious code on the computers of people using Tor and possibly other users of the Firefox browser, officials of the anonymity service confirmed Tuesday."
Mozilla devs are working on a fix. But till then, do switch to other browsers temporarily.
"A representative of Mozilla said officials are aware of the vulnerability and are working on a fix. While the vulnerability was already being actively exploited, the publication of the complete source code now puts it in the hands of a much wider base of people. Until a patch is available, Firefox users should use an alternate browser whenever possible, or they should at the very least disable JavaScript on as many sites as possible."