Hello RIDOCK,

Kaspersky Protection hasn't worked with even older Firefox versions .....

It would be best to always use the latest Firefox version, for many reasons.

May I suggest to forget about Kaspersky altogether  ?

You're best off with just using Windows built-in Defender and maybe let malwarebytes run a scan once a month. With that and using the best browser on the planet, it's like being in Fort Knox   …..

Also see :

https://www.howtogeek.com/239950/dont-use-your-antivirus-browser-extensions-they-can-actually-make-you-less-safe/

And :

http://tech.firstpost.com/news-analysis/ex-mozilla-firefox-developer-says-anti-virus-software-does-more-harm-than-good-359798.html

McCoy,the answer you have given has no relevance to my question ! Rely on Windows antivirus plus a Malwarebytes scan now and again ? What a hoot!! If you are in the top 10 I may have to give this forum a miss! RIDOCK

Your question is :

" Can I use The Kaspersky Protection add on in Firefox 64
(Windows 7) "

My reply :

"Kaspersky Protection hasn't worked with even older Firefox versions ..... "

That does not answer your question  ?

I could of course have left out the rest of my post - merely wanted to give you some additional information (with only your best interest at heart).

RIDOCK said

What a hoot!! If you are in the top 10 I may have to give this forum a miss! RIDOCK

I have always hated that   "Top 10 contributor"   under some contributors names :   it's all about the number of posts,   ergo :  it's about   quantity   and not   quality   .....

There are plenty of other contributors here who will be able to give you the answer that I couldn't.