OK, so there’s already an updated version that fixes the problem. But there is (was?) a problem!
It seems that Firefox was invincible because no one was attacking it. Now there are 25 million Firefox users. Now there are exploits.
For the record, I occasionally use Firefox myself. It is a fine browser, although I’m not a fan of tabbed browsing. I’m primarily a Microsoft fan, but have a few open source items that I use and appreciate.