Steps to reproduce:

1. Extract the PoC files from the tarball somewhere;
2. Run "python3 -m http.server 9001" (or similar);
3. Subscribe to feed http://localhost:9001/feed.xml in Liferea;
4. Edit subscription properties to enable option "Extract full content from HTML5 and Google AMP";
5. Update the feed at the source (for example, copy feed-updated.xml over feed.xml);
6. Update the subscription in Liferea;
7. Check the results in files /tmp/bad-item-link.txt and /tmp/bad-amp-url-item*.txt.