I’m a fan of FOSS and reasonable privacy with data. I also often look for and install software on my computers for random tasks as they come up. Today, when I was looking to install an extension to Firefox called Wikipedia-EN that helps me search Wikipedia by highlighting a word, the Mozilla page for the extension states:

This add-on is not actively monitored for security by Mozilla. Make sure you trust it before installing.

As someone that is not educated in programming or perpetually current on tech news, what can I do to assess the safety of this and other software? Is there a site that transparently evaluates software and publishes its findings?