This is a vulnerability in a non-Atlassian Jira Software dependency. Atlassian's application of this dependency presents a lower, non-critical assessed risk.

This Critical severity Prototype Pollution vulnerability known as CVE-2021-39227 was introduced in 10.3.0, and 11.0.0 of Jira Software Data Center and Server.

This vulnerability with a CVSS Score of 9.8 and a CVSS Vector of CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H allows an unauthenticated attacker to take actions which have a high impact to confidentiality, high impact to integrity, high impact to availability, and requires no user interaction. 

Atlassian recommends that Jira Software Data Center and Server customers upgrade to latest version, if you are unable to do so, upgrade your instance to one of the specified supported fixed versions:

• Jira Software Data Center and Server 10.3: Upgrade to a release greater than or equal to 10.3.14
• Jira Software Data Center and Server 11.0: Upgrade to a release greater than or equal to 11.3.0

See the release notes. You can download the latest version of Jira Software Data Center and Server from the download center.

The National Vulnerability Database provides the following description for this vulnerability: ZRender is a lightweight graphic library providing 2d draw for Apache ECharts. In versions prior to 5.2.1, using `merge` and `clone` helper methods in the `src/core/util.ts` module results in prototype pollution. It affects the popular data visualization library Apache ECharts, which uses and exports these two methods directly. The GitHub Security Advisory page for this vulnerability contains a proof of concept. This issue is patched in ZRender version 5.2.1. One workaround is available: Check if there is `{}proto{}` in the object keys. Omit it before using it as an parameter in these affected methods. Or in `echarts.util.merge` and `setOption` if project is using ECharts.