Issue Summary

Using square brackets in the file name will cause the generated link to be broken after upload.

Environment

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Steps to Reproduce

1. Create an attachment with square bracket (" [ " & " ] ").
2. While commenting on an issue, upload the attachment.
3. You will see the link is broken as shown in Actual Results.

Expected Results

Actual Results

Notes

• The file gets uploaded nonetheless.
• This is no filename spaces bug regression as an attachment with spaces in their name attached fine:
  

Workaround

Workaround 1
Use another markup syntax but escaping the square bracket with a backslash symbol:

[filename to be displayed by escaping the square bracket | link to the file by copy-paste from the attachment section] 

Example:

[some file with \[square bracket\].msg|http://baseURL/secure/attachment/12345/some%20file%20with%20%5Bsquare%20bracket%5D.msg]

Workaround 2
Upgrade to JIRA 7.13.4 (tested alright) and above.