Issue Summary

Starting on UPM 6.3.5 (bundled with Jira 9.12.8+), the version and platform incompatibility warnings displayed on the Manage Apps page show a broken HTML rendering for the “Learn more" link.

The “Learn more" links in UPM 6.3.4 work fine.

This is reproducible on Data Center: yes

Steps to Reproduce

1. Install an incompatible (version/platform) app.
2. Access the "Manage apps" page and wait for the warning to load.

Expected Results

Have the "Learn more" link rendered correctly.

Actual Results

The "Learn more" link does not render correctly, displaying HTML tags on the UI, such as below.

An installed app is not approved for Data Center. Only apps meeting a set of performance requirements for large, clustered environments are approved for Data Center. <a href="https://www.atlassian.com/licensing/data-center-approved-apps" target="_blank">Learn more</a>

Workaround

To avoid the rendering issues, you can downgrade UPM to version 6.3.4, however, to do so requires a cold restart of the Jira cluster.
Since the rendering error only affects "Learn more" links on the Manage Apps page, its impact is minimal for Jira's functionalities and can safely be ignored until a fix is released.

1. Shut down Jira on all cluster nodes.
2. Download UPM 6.3.4 from the UPM Version History page.
3. Place a copy of the downloaded jar file in the '<Jira_Installation>/atlassian-jira/WEB-INF/atlassian-bundled-plugins' directory for each node in the cluster.
4. Remove the 'atlassian-universal-plugin-manager-plugin-6.3.5.jar' file from the above directory.
5. Be sure to also remove any similarly named file (may be prepended by a number or string) from:
   • '<Jira_home>/plugins/installed-plugins'
   • '<Jira_shared_home>/plugins/installed-plugins'
6. Start the Jira nodes one by one.