A vulnerability in multiple Atlassian products allows a remote, unauthenticated attacker to cause additional Servlet Filters to be invoked when the application processes requests or responses. Atlassian has confirmed and fixed the only known security issue associated with this vulnerability: Cross-origin resource sharing (CORS) bypass. Sending a specially crafted HTTP request can invoke the Servlet Filter used to respond to CORS requests, resulting in a CORS bypass. An attacker that can trick a user into requesting a malicious URL can access the vulnerable application with the victim’s permissions. Atlassian Bamboo versions are affected before 8.0.9, from 8.1.0 before 8.1.8, and from 8.2.0 before 8.2.4. Atlassian Bitbucket versions are affected before 7.6.16, from 7.7.0 before 7.17.8, from 7.18.0 before 7.19.5, from 7.20.0 before 7.20.2, from 7.21.0 before 7.21.2, and versions 8.0.0 and 8.1.0. Atlassian Confluence versions are affected before 7.4.17, from 7.5.0 before 7.13.7, from 7.14.0 before 7.14.3, from 7.15.0 before 7.15.2, from 7.16.0 before 7.16.4, from 7.17.0 before 7.17.4, and version 7.21.0. Atlassian Crowd versions are affected before 4.3.8, from 4.4.0 before 4.4.2, and version 5.0.0. Atlassian Fisheye and Crucible versions before 4.8.10 are affected. Atlassian Jira versions are affected before 8.13.22, from 8.14.0 before 8.20.10, and from 8.21.0 before 8.22.4. Atlassian Jira Service Management versions are affected before 4.13.22, from 4.14.0 before 4.20.10, and from 4.21.0 before 4.22.4.