Certificate Trust от devmni

This add-on shows with a colored icon, whether the SSL/TLS certificate currently used by the website for the HTTPS connection is classified as trustworthy by Mozilla or only by the local computer, or if it is only self-signed or a http connection. It helps, for example, to recognize (company) proxies, which are also displayed by Firefox with a green lock by default.

https://github.com/devmni/Certificate_Trust