Cart66 Affecting RSS Feed

I’m using Cart66 Lite on WordPress 3.5.1 and it is screwing up my RSS feed.

For some reason it appears to be inserting a buy button in to my RSS feed (www.musicforchange.com/feed) which is making the feed invalid.

You can see this at https://validator.w3.org/feed/check.cgi?url=http%3A%2F%2Fmusicforchange.com%2Ffeed

If I look at the feed itself there are all sorts of references it this Mijireh payment system in the RSS feed.

How can I stop this from messing up my RSS feed?

Thanks for your help

Jason

https://www.ads-software.com/extend/plugins/cart66-lite/