Issue Summary

This is reproducible on Data Center: yes

According to the official documentation, attachment names can't contain any of the characters below: 

'\', '/','\"', '%', ':', '$', '?', '*'.

However, Jira allows adding attachments with names containing the above characters in specific scenario

Steps to Reproduce

Tested on Windows Server 2022, Windows Pro 11

When trying to add an attachment with unsupported characters in a filename by drag&drop or Browse dialog, Jira will expectedly throw the error like below:

But when using the following approach, Jira will add the attachment:

1. Open up an issue in JIRA. The issue must have an attachment section.
2. Open a Snipping Tool 
3. Take a picture snip
4. At Snipping Tool, right-click on the image > Copy
5. Go back to the JIRA issue with the attachment section.
6.  Using the keyboard, press CTRL+V.
7. A dialog box appears
   
8. Enter the name with unsupported characters into the 'File name' field and click Upload

Expected Results

Attachment is not added, and the error about the special characters (as above) is thrown

Actual Results

The attachment with unsupported characters is being added to the issue

For the attachments with any unsupported character in the filename, Jira will show the thumbnail in the Attachments section correctly

Attachments with characters:

can be viewed and downloaded without any issues

show the below error when trying to open:
 
Also, these attachments can't be downloaded

Workaround

Avoid using special characters in attachment filenames