This Template Injection vulnerability allows an authenticated attacker, including one with anonymous access, to inject unsafe user input into a Confluence page. Using this approach, an attacker is able to achieve Remote Code Execution (RCE) on an affected instance. Publicly accessible Confluence Data Center and Server versions as listed below are at risk and require immediate attention. See the advisory for additional details

Atlassian Cloud sites are not affected by this vulnerability. If your Confluence site is accessed via an atlassian.net domain, it is hosted by Atlassian and is not vulnerable to this issue.