There appears to be a bug in iTunes, whereby if a podcast episode’s enclosure gets redirected to another URL, iTunes will update the podcast’s URL.

I discovered this this morning when starting up iTunes: my Mimsy Were the Borogoves podcast had the nice big exclamation point next to it. On looking at the “info” button, the URL for Mimsy’s RSS feed had changed from the Mimsy podcast URL to the Persistence of Vision PDF tutorial URL! It had gone from http://www.hoboes.com/Mimsy/?RSS to http://www.hoboes.com/html/NetLife/POV_Simple/POV_Simple.pdf!

I often link to smaller URLs. In this case, I link to the tutorial as http://www.hoboes.com/NetLife/POV_Simple/POV_Simple.pdf. The web server automatically redirects /NetLife to /html/NetLife.

A little testing verified that whatever the /NetLife folder redirected to, iTunes would change the podcast’s URL from its correct URL to that one as soon as I downloaded the tutorial!

So if people are putting your media into their podcasts, it sounds like you’ve got a nice, easy way to hijack their podcast feed. Just redirect to your own podcast.

This may also cause trouble in the future, as enclosures disappear; some sites will redirect failed links to a failed link page. In this case, anyone downloading an old episode will find that the podcast's URL has changed to the failed link page’s URL!

The problem is augmented by the inability, in iTunes, to manually change a podcast’s URL. You need to remove the old podcast and then resubscribe.

I’ve submitted this as a bug to Apple. In the meantime, you might not want to download the Persistence of Vision tutorial through iTunes. Either hit the link in your web browser, or use a different RSS reader.