Problem

Image attachments do not display inline in wiki renderer fields when using the wiki markup such as !image.png! in a JIRA issue. For example:

Diagnosis

All other wiki markup appear to be working fine e.g. [^image.png]. (But you may also have interference with other wiki markup next to the image.)

 If the case is that no wiki markup is working at all, you may want to look at this other KB article instead: Wiki markup does not work in text or comment field

Cause

In JIRA's General Configurations Settings, the option "Internet Explorer MIME Sniffing Security Hole Workaround Policy" has been set to "Secure: forced download of attachments for all browsers". When set to 'secure' this disables the ability to render any attachments inline without downloading, including images unfortunately. This applies to all browsers. 

There was a suggestion raised in  JRA-43914 - Getting issue details... STATUS  to remove this as IE7 is no longer supported, but it was deemed to be a still necessary security measure but not directly related to just IE7 anymore. Instead  JRASERVER-45348 - Getting issue details... STATUS was raised to rename the setting to a more appropriate name.

Workaround

To display inline images in JIRA fields try set the "Internet Explorer MIME Sniffing Security Hole Workaround Policy" option to either "Insecure: inline display of attachments" or "Work around Internet Explorer security hole".

Cloud customers might have to contact the Atlassian Support to have the workaround applied.