All On-Prem Confluence versions are currently impacted by CWD-5803. As of the writing of this bug the latest version of Confluence 7.20.0 includes Embedded Crowd 5.0.0.

The only workaround at this time is to try and limit what groups/users are synced in (Query to Check Groups Actively Used in Space Permissions and Page Restrictions is a good place to start), but even with that some applications could see intermittent full garbage collection as a result of syncs.