NEW FIREFOX 51.0.1 26 January 2017 To get click on Help>About Firefox>Check for Updates (size varies) release notes https://www.mozilla.org/en-US/firefox/51.0.1/releasenotes/
... And Malwarebytes.
Thanks! Jim fixed Its not just Mozilla/Firefox look at Microsoft.
Your title is wrong. Should be 51.0.1.
Thanks for the update.
Mozilla needs better quality control before releasing buggy code.
Jim