Escalating XSS in PhantomJS Image Rendering to SSRF/Local-File Read

I recently came across across a request on a bounty program that took user input and generated an image for you to download. After a little bit of a journey, I was able to escalate from XSS inside of an image all the way to arbitrary local-file read on the server. It’s a private program, so I’m going to do my best to redact as much information as possible.

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