[Vulnerability] External Link Bypass

Using a script and some very sneaky CSS, a user can make another user think a link is an innocent link. I listed some of the other bad sneaky stuff a user can do with that on the program it's hosted on.
https://www.khanacademy.org/computer-programming/danger-script/6527297851752448
If you click on the link it skips KA's link filter and goes straight to my site. Not really good. And the user can't see what the link is or what it's for until they either look at the code or click it.

Reproduce the behavior using the linked Khan Academy program and verify that an external link bypasses the filter while being visually disguised by CSS. Then locate the live-editor link-filtering entry point and add a regression test covering the bypass; done means the link is identified or blocked before navigation.

Written by the indexing model from the issue text.