How to restrict attachment file type?

I stumbled on this older question, and I thought I'd answer it in case others did the same.  This post discusses how to change the attachment size limit for work items:  https://jazz.net/forum/questions/1523/attachment-size-limit-for-work-items

One thing you could try is extending RTC, creating a work item save precondition (advisor). I am not sure if you can prevent the upload, but it might be an option.

This code shows a follow up ation: https://rsjazz.wordpress.com/2012/07/31/rtc-update-parent-duration-estimation-and-effort-participant/ and a participant is almost the same code. https://rsjazz.wordpress.com/2012/11/01/restrict-delivery-of-changesets-to-workitem-types-advisordelivery-of-changesets-associated-to-wrong-work-item-types-advisor/ talks about an advisor (but for deliver) and also talks about the differences.