Security fixes go into the latest release only. Please update to it before reporting a problem.
Please report security problems privately, not in a public issue: on GitHub, open the repository's Security tab and choose Report a vulnerability. Include the output of rekopub -VERSION, the command you ran, and what happened.
You should get a reply within a week. Once a fix is released, the report is published as a security advisory, with credit to you unless you prefer otherwise.
ReKoPub downloads web pages chosen by its user, which are untrusted input. Problems in scope include:
-URL is on the internet;What ReKoPub does to stay safe is described under Privacy and security in the README.