I had this same problem, however I uninstalled 360 totally and then reinstalled it from their website. I then installed the FF add-on from the 360 website and it went in flawlessly.. The strange thing is that the revision level went backward (from 1005 to 1004) when I installed the plug in from the 360 website however the update date went forward to July 25 2017 (today) . Hmmm

Complete protection is paramount with online activity.

Cool.

Nice job

Very good

Very easy to get along with this program...

User hk
4 Engine is a really good basis.
viruses and internet is becoming much more dangerous than 20 years before. But in this old time most people was to unserios in handling with computer -may today same (a lot of new technik egg smartphones tabletts...)- every medium must be av-checked, downloads too.......
here 360 helps very much in an easy way, and checking all files (archives too -without limites....)....
performens keeps -in my opinion- very good, i'm using an old system............
thank you 360

Thank you for the sharing this security extention.