It's time for another patch day, SUPEE-7405 for Magento 1.x is out and the list of fixes is long: https://magento.com/security/patches/supee-7405
After the experience with the last patches, I have to ask again: what are the possible problems when applying the patch and what do I need to consider?
Lots of XSS issues were fixed again, so I expect to patch custom themes manually. Anything else? Are there backward incompatible changes?