Firefox - Your connection is not secure

[uninfected1]

I've just reinstalled Firefox having not used it for several years and I'm getting this message when I try to connect to a lot of sites, including MalwareTips. Chrome connects to them with no problem.

This is the whole message, in this case for MalwareTips, but It's the same for a lot of sites.

Your connection is not secure

The owner of malwaretips.com has configured their website improperly. To protect your information from being stolen, Firefox has not connected to this website.

Learn more…

malwaretips.com uses an invalid security certificate.

The certificate is not trusted because the issuer certificate is unknown.
The server might not be sending the appropriate intermediate certificates.
An additional root certificate may need to be imported.

(Error code: sec_error_unknown_issuer)

Clearly there's nothing wrong with MalwareTips because I get this message with many popular sites , but I don't know what's causing the problem. I've done a number of things as suggested to other people with this issue such as refresh Firefox, uncheck Hardware Acceleration, delete the cert8 file, and disable my antivirus and firewall, but I still get the same Firefox message, so any help would really be appreciated.

 

[Deleted Member 333v73x]

I've just returned to Firefox and I'm getting this message when I try to connect to a lot of sites, including MalwareTips. Chrome connects to them with no problem.

This is the whole message, in this case for MalwareTips, but It's the same for a lot of sites.

Your connection is not secure

The owner of malwaretips.com has configured their website improperly. To protect your information from being stolen, Firefox has not connected to this website.

Learn more…

malwaretips.com uses an invalid security certificate.

The certificate is not trusted because the issuer certificate is unknown.
The server might not be sending the appropriate intermediate certificates.
An additional root certificate may need to be imported.

(Error code: sec_error_unknown_issuer)

Clearly there's nothing wrong with MalwareTips because I get this message with many popular sites , but I don't know what's causing the problem. I've done a number of things as suggested to other people with this issue such as refresh Firefox, uncheck Hardware Acceleration, delete the cert8 file, and disable my antivirus and firewall, but I still get the same Firefox message, so any help would really be appreciated.

Can you upload a screenshot, maybe a malicous extension.

 

[illumination]

Have you checked to see if Adguards CA is in firefox?

Connection is not trusted - Firefox - Powered by Kayako Fusion Help Desk Software

 

[Deleted member 2913]

The prob can happen on Firefox with any products that installs their own certificates to scan/filter HTTPS connections.

I have noticed this with Eset, Kaspersky, Avast & AdGuard especially AdGuard...And on Firefox only & especially portable Firefox...didn't noticed with IE, Chrome & Vivaldi Portable.

 

[uninfected1]

Have you checked to see if Adguards CA is in firefox?

Connection is not trusted - Firefox - Powered by Kayako Fusion Help Desk Software

You got it spot on first time illumination. Easy to sort out with your link. Fortunately the easy fix worked so didn't have to mess around with certificates - just closed Firefox, disabled Adguard, reenabled it, opened Firefox and everything's fine. Really appreciated.