A Hacker Hid a Message Inside a Trusted TLS Certificate
Horible public key tricks
Maurycy Z. got tired of the ACME dance and decided to protest by crafting a vanity RSA key whose modulus spells out a readable message in base64, then had Let's Encrypt sign it. The trick: tweak the upper half of n, round q up to the next prime, and the embedded text survives. The result is a fully functional, trusted certificate with a joke baked into its public key.
No one checks these things. A certificate authority got away with the number 4 for a year.