There was a man-in-the-middle (MITM) vulnerability present in the Confluence Previews plugin in Confluence Server and Confluence Data Center. This plugin was used to facilitate communication with the Atlassian Companion application. The Confluence Previews plugin in Confluence Server and Confluence Data Center communicated with the Companion application via the atlassian-domain-for-localhost-connections-only.com domain name, the DNS A record of which points at 127.0.0.1. Additionally, a signed certificate for the domain was publicly distributed with the Companion application. An attacker in the position to control DNS resolution of their victim could carry out a man-in-the-middle (MITM) attack between Confluence Server (or Confluence Data Center) and the atlassian-domain-for-localhost-conn