There isn't a way to restrict the attachments people can upload, by blacklisting a file type. I've found this request on our issue tracker, closed as "won't fix":
There are some suggestions that may be useful in this post:
I hope this helps!
The "solved" flag is for "there's an answer that tells us nothing else needs doing". Mostly that means that the original question has an answer, but it can also mean "closed because there is no answer", or, as in this case, "closed because there's an issue which tells you the state of the request"
More and more people are building their careers with Atlassian, and we want you to be at the front of this wave! Important Dates Start the Certification Prep Course by 2 April 2019 Take your e...
Connect with like-minded Atlassian users at free events near you!Find a group
Connect with like-minded Atlassian users at free events near you!
Unfortunately there are no AUG chapters near you at the moment.Start an AUG
You're one step closer to meeting fellow Atlassian users at your local meet up. Learn more about AUGs