Proof of Concept or GTFO issue 0x14 is a PDF document file that can also be run as a NES ROM. The file will display its own MD5 hash in a PDF viewer, and also displays its own MD5 hash in a NES emulator (only first 40KB+16 bytes are actually loaded there)

https://github.com/angea/pocorgtfo#0x14

And yes, documents are not normally supposed to be able to display their own MD5 hash.