When attaching an external file to an issue page, if the image file name includes a JIRA ticket ID (e.g. "my-image-for-issue-ABC-123.png"), that will prevent the thumbnail image from being rendered in a comment on that issue. This was the case when using an ID to a resolved issue, though it's possible that any issue ID could cause trouble.
Workaround: Replace the hypen in the ticket ID present in the file name with an underscore ("my-image-for-issue-ABC_123.png").
JIRA version:
- v7.0.11#70121-sha1:19d2497
