On Jira version 11 when you access Administration > System > Email Templates you see a Warning:

Starting with Jira 10.0, we've introduced security enhancements for Velocity templates and allowlists. These updates prevent the use of any Velocity templates that aren?t explicitly included in the allowlist. This restriction also applies to admin-provided batched email notification templates.

To enable this feature, add the following lines to your (JIRA-INSTALL-DIR)/atlassian-jira/WEB-INF/classes/velocity-default.properties file. Start at line 1000:

This is related with https://jira.atlassian.com/browse/JRASERVER-78661

However even after applying the suggested workaround this warning is still displayed on the UI.

There should be an option to dismiss the warning or it should disappear after the workaround is applied.