Rated 1 out of 5 stars

Both Norton and Malwarebytes detected it, and not just as a PUP or PUM! What is the deal with that???

This review is for a previous version of the add-on (0.4.6).  This user has a previous review of this add-on.

Binary patching is indeed a kind of suspicious behavior that some anti-virus software would complain, but that doesn't mean it's malicious.
BTW I'm not the author of the binary patch. According the author, this patch is created using diablo2oo2's Universal Patcher. You can download the project files and create the patcher yourself: http://sourceforge.net/projects/pcxfirefox/files/Tools/RemoveFx41x64PluginRestrict/dup2project/