Application Links before version 5.0.11, from version 5.1.0 before 5.2.10, from version 5.3.0 before 5.3.6, from version 5.4.0 before 5.4.12, and from version 6.0.0 before 6.0.4 allows remote attackers to inject arbitrary HTML or JavaScript via a cross site scripting (XSS) vulnerability in the applinkStartingUrl parameter. The product is used as a plugin in various Atlassian products where the following are affected: Confluence before version 6.15.2, Crucible before version 4.7.0, Crowd before version 3.4.3, Fisheye before version 4.7.0, Jira before version 7.13.3 and 8.x before 8.1.0.

The ListEntityLinksServlet resource in Application Links before version 5.0.12, from version 5.1.0 before version 5.2.11, from version 5.3.0 before version 5.3.7, from version 5.4.0 before 5.4.13, and from version 6.0.0 before 6.0.5 disclosed application link information to non-admin users via a missing permissions check.

The OAuthHelper in Atlassian Application Links before version 5.0.10, from version 5.1.0 before version 5.1.3, and from version 5.2.0 before version 5.2.6 used an XML document builder that was vulnerable to XXE when consuming a client OAuth request. This allowed malicious oauth application linked applications to probe internal network resources by requesting internal locations, read the contents of files and also cause an out of memory exception affecting availability via an XML External Entity vulnerability.