A problem occured after using a netscaler (for TLS communication) which forces an authentification for accessing Jira.
e.g. Agile Cards via Instaprinta don't show the issuetype or priority icons (changing icons which depends on config). Therefor we found some sites which are accessable without any kind of authentification
Sites like [JiraURL]/secure/viewavatar?size=xsmall&avatarId=10316&avatarType=issuetype don't need auth.
Same goes for sites like [JiraURL]/images/icons/
Some other Sites you know about?
