You will need to update to Firefox 66.0.4. After doing so, if you desire to use Adobe Flash, than you should install the latest version of Flash. https://get.adobe.com/flashplayer/

You should use the updated version anyway, it is not safe to remain on older versions of Firefox or Flash

I'm not sure if there will be any official fix for archaic versions, but you can find a solution here: [unsafe link removed]

Please ignore the link above. As I said, all your software will work in a new version, and you should update ASAP

Thank you Tyler Downer and TyDraniu for the replies. I hope for a update-less solution though.

So what I'm telling you is that you really really need to update to 66.0.4. 54.0.1 is not secure, and the newer version will work just fine. Please update ASAP.

I gave in and updated and am on 66.0.4 and everything works at least for me.

See these threads about to add the certificate manually:

• /questions/1258208 plugins could not be verified firefox esr 52
• /questions/1258275 How do I re-enable the add-ons WITHOUT being forced to upgrade

See also Mozilla Add-ons on Twitter:

• https://twitter.com/mozamo/

It looks that there is a system Add-on planned for older Firefox version that do not support the hotfix.

• Bug 1549604 - ship legacy system add-ons to remediate armagadd-on 2.0

(please do not comment in bug reports
https://bugzilla.mozilla.org/page.cgi?id=etiquette.html)

Corel, the op already updated and said Firefox works

Others may read this thread if they see its title.

Hello, thank you again for the replies. Tyler Downer's solution of updating did work for me, as I don't use any modifications and don't use many add-ons, I will flag however cor-el's response as the solution, as it provides a solution without updating, which was the original idea and some people might just want to keep an older version and are aware of the consequences. (Edited my previous posts accordingly.)