Window Opener Property Bug

How it was found

The bug mentioned in #23386 is not yet correctly patched I believe.

See, if a user sets his/her profile's website link to a similar page as mentioned in #23386. I mean a page that can manipulate the window.opener property would be able to accomplish similar results as in #23386

Proof-of-Concept:

1. Login to HackerOne
2. Navigate to https://hackerone.com/settings/profile/edit
3. Set Website to https://demo.prakharprasad.com/ga.html
4. Once someone visits this link from a profile page (eg. https://hackerone.com/<username->), his opener HackerOne window will be hijacked.

Let me know if you have any questions.

Thanks, Prakhar Prasad