Depends on https://bugzilla.mozilla.org/show_bug.cgi?id=1054379. Passing the URL and blocked nodes should happen as URL fragments so that populating the form doesn't automatically send information to whatever the endpoint is until the user clicks "Submit"

(In reply to [:mmc] Monica Chew (please use needinfo) from comment #0) > Depends on https://bugzilla.mozilla.org/show_bug.cgi?id=1054379. > > Passing the URL and blocked nodes should happen as URL fragments so that > populating the form doesn't automatically send information to whatever the > endpoint is until the user clicks "Submit" Right. We could use JSON to package the top-level URL along with the URLs of blocked elements (see document.blockedTrackingNodes) and any other meta-data and append everything as a fragment identifier to the URL that will return the page with the submission form. The submission page could then use JS to retrieve it's own URL (document.location.href) and extract the fragment identifier, parse the JSON blob and populate the submission form. The browser will strip the fragment identifier from the submission page URL when making the request for it.

Blair suggested using a pref to fill this URL, setting it empty by default then not showing the link until the pref is full so turning on the link is a one-liner.