I provided more explanations about this add-on as suggested by our users.

* Added a list of allowed URLs to ensure user privacy (only allowed URLs are sent to the cKnowledge.io search engine): https://github.com/gfursin/ck-browser-addon-firefox/blob/main/js/background.js#L8
* Updated purify.min.js library to avoid recently discovered vulnerabilities (as suggested by Mozilla colleagues)

We now sanitize external HTML to avoid malicious code (thanks to a reviewer's suggestion).