If you load a page with your SSN, the full page will probably be parsed by the extension in search of a "GoLink". Honestly, that's pretty unavoidable. The parser most likely needs to read every byte on the page to see if its part of a GoLink, and that includes the segment of bytes that includes your SSN.

Any ad-blocker or otherwise page-modifying Chrome Extension requires the same permissions and likely does the same thing.

Provided the GoLinks extension isn't phoning home with the full contents of the pages its parsing, and immediately discards non-GoLink related data, this shouldn't be a problem.

It would be nice if the GoLinks team could clarify exactly what data is sent back to their servers by the Chrome Extension.

Chrome Extensions can also be inspected and their network traffic can be sniffed quite easily, so independent auditing is possible as well.