Steps to reproduce:

1. Extract the PoC files from the tarball somewhere;
2. Run "python3 -m http.server 9001" (or similar);
3. Try to subscribe to http://localhost:9001/ in Liferea;
4. Liferea will show a parsing error (expected), but feed auto-discovery
   already created and ran a command feed source that created file
   /tmp/bad-feed-discovery.txt