Extensions return ERR_SSL_PROTOCOL_ERROR, cannot log in with 2-factor authentication after update to Plesk Obsidian 18.0.61

Symptoms

• Error is displayed in different Plesk extensions, e.g. on the Monitoring page or when publishing domains via SiteJet:

  ERR_SSL_PROTOCOL_ERROR

• With authentication extension enabled (e.g. Multi-Factor Authentication (MFA) or Google Authenticator), accessing Plesk via login link redirects to port 8880:

  https://example.com:8880/modules/mfa/index.php/index/auth?return

Cause

A known Plesk issue that is going to be fixed in the nearest update.

Resolution

As a workaround, until the bug is fixed, substitute port 8880 in URLs that return errors with 8443 like so:

https://example.com:8443/modules/mfa/index.php/index/auth?return

Additional information

Unable to log into Plesk using one time link after Plesk update to 18.0.61: Incorrect redirection to port 8880