https://www.bleepingcomputer.com/news/security/this-image-contains-its-own-md5-checksum-and-its-kind-of-a-big-deal/

Generating checksums—cryptographic hashes such as MD5 or SHA-256 functions for files is hardly anything new and one of the most efficient means to ascertain the integrity of a file, or to check if two files are identical.

However, generating a file containing its own checksum as part of its content is a task quite daunting, if not seemingly impossible due to a paradox involved in the process.