Image attachments are not displayed inline in wiki renderer fields
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:
All other wiki markup appear to be working fine e.g. [^image.png].
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
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.
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.