Inconsistent MIME Type when Attaching a Screenshot in JIRA

Problem.

Different methods of attaching a screenshot in JIRA results to an inconsistent MIME type.

Steps to Reproduce the issue

A. Scenario A.

1. Open an issue
2. Capture a screenshot and save it to the clipboard by pressing Ctrl + PrtScn keys in Windows
3. Click anywhere within an issue detail page
4. Press Command + V to show the Attach Screenshot screen
5. Click Upload

B. Scenario B.

1. Open an issue
2. Capture a screenshot and save it to the clipboard by pressing Ctrl + PrtScn keys in Windows
3. Click on either Description or Comment field
4. Press Command + V to paste the image

Expected behaviour

The MIME Type should be the same regardless of the method you attach the screenshot.

Actual behaviour

• Scenario A
  The MIME type is image/png
• Scenario B
• The MIME type is text/plain
  

NOTES:

• Screenshots attached in both scenarios A and B can be viewed in Chrome without any issue.
• Screenshots attached using scenario B can't be viewed in IE 11. It appears to be a broken image.

Environment

Windows
JIRA 7.3.7