Open Redirect on http://events.hackerone.com/redirect?url=https://naglinagli.github.io

Summary

@nagli found an open redirect vulnerability in a 3rd party vendor that was used by HackerOne. This system did not contain any data related to reports submitted and stored on hackerone.com. HackerOne worked with the vendor to remediate the vulnerability. The report is partially disclosed to anonymize the vendor.

This vulnerability is part of a study I have been conducting about "Vulnerability inheritance - Attacking companies and scoring bounties through 3rd party integrations". events.hackerone.com was pointing towards a 3rd party vendor as a CNAME, I managed to find Open Redirect on an endpoint which belongs to the vendor via ?redirect parameter that allowed me to achieve Open Redirect on Hackerone's subdomain.