Christian contributed to the spatie/laravel-csp repository by developing three new Content Security Policy (CSP) presets for Intercom, Google TLDs, and Posthog, each implemented as dedicated PHP classes with comprehensive README documentation. He enhanced backend security by expanding CSP options and refactored domain configuration logic to reduce misconfigurations and streamline developer experience. Using PHP and PHPUnit, Christian improved test coverage by introducing snapshot tests that validate CSP directives for all new presets. His work demonstrated depth in backend development and security, focusing on maintainable code, clear documentation, and robust testing practices to ensure reliable and secure CSP integrations.