Quick Page Notes od Alejandro Nicolas

Quick Page Notes helps you keep lightweight research without leaving the page. Click the toolbar button or the Save selection button in the popup to highlight the current selection and store it per site. Notes appear in the popup with the original link and timestamp. You can choose Firefox Sync to access notes across devices or local storage to keep them on this computer. The add-on requests only the minimum permissions needed to work reliably and does not load any remote code.
The extension injects a small content script only in direct response to a user action, using the active tab permission that’s granted when you open the popup or click the toolbar icon. The script wraps the selected text in a visible highlight and sends the text and URL to the background script, which stores it under the current site. There are no inline scripts, no eval, and no external resources. Options let you switch between Sync and local storage at any time.