Your scanner just found include.html - but what does the javascript do?

Challenge Information

This is a re-created bug I recently found on a public bugbounty program. My scanner was hunting for interesting subdomains&files and I noticed one interesting subdomain which contained nothing but javascript. After analysing the code I managed to find a bug, so this challenge is: can you successfully read what the javascript code is doing and find what I found?

Note: The code is recreated but works exactly the same as the program I found it on. :)

Challenge Solutions

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