Atlassian Jira allows server side template injection (SSTI) vulnerability.
There was a server-side template injection vulnerability in Jira Server and Data Center, in the ContactAdministrators and the SendBulkMail actions. An attacker is able to remotely execute code on systems that run a vulnerable version of Jira Server or Data Center. All versions of Jira Server and Data Center from 4.4.0 before 7.6.14, from 7.7.0 before 7.13.5, from 8.0.0 before 8.0.3, from 8.1.0 before 8.1.2, and from 8.2.0 before 8.2.3 are affected by this vulnerability.
You have to update to latest version.