This ticket may not be in the right place; I couldn't find where to report bugs in support.atlassian.com itself, but since it appears to be based on Jira, I created it here.

Please forward this issue to the right team if possible.

Thanks!

In https://support.atlassian.com/requests/BBS-188046/ , I had attached a screenshot with the filename

backend Config [Jenkins].png

The editor inserted this markup: 

[backend Config [Jenkins].png|https://getsupport.atlassian.com/servicedesk/customershim/secure/attachment/7628613/7628613_backend+Config+[Jenkins].png?fromIssue=5151367] 

It would be better if the square brackets were escaped, although the exact character sequence may be a challange to figure out.