HackerOne: Indexing of urls on the "External link warning" pages discloses many vulnerable endpoints from the past and unlisted videos/photos

@nagli found a misconfiguration in an interstitial page that could lead to a link to be indexed by a 3rd party. This could have exposed links to proof of concepts that HackerOne users had posted on hackerone.com. This affected a specific set of customers, which HackerOne worked together with to...