I know almost nothing about the add-on SDK, so please see bug 607601 for details. Bug 642306, bug 646575 and bug 649334 are similar and hopefully will also be fixed soon too. Great work by Alexandre Poirot!
(And if anyone who does know about the add-on SDK can explain a bit more about these leaks and which add-ons are affected, I’d love you to do so in the comments. Thanks!)