Brikit Calendar Integrations 1.2.1 is a bug fix release and is a recommended update for all Calendar Integrations users running Confluence 7.20.3 or earlier.
Atlassian released a security vulnerability fix that broke all macros and templates in all Brikit products.
This will affect all customers that upgrade to any of the Confluence versions listed as patches for the vulnerabilities announced on December 6. Calendar Integrations 1.2.1 fixes this for all versions of Confluence earlier than 8.0.
See the Calendar Integrations 1.2.1 Release Notes for details.