Worked on the mattermost/mattermost repository to deliver CommandResponse validation and security enhancements for backend command handling. Focused on strengthening API reliability by implementing strict validation logic, expanding test coverage for edge cases, and introducing robust logging for invalid responses. Hardened URL validation for goto_location fields to mitigate XSS risks, ensuring only http and https schemes are accepted. Updated the validation flow to guard against nil CommandResponse values and improved UTF-8 character handling. The work was carried out using Go and involved backend development and testing, resulting in more secure and resilient command processing within the Mattermost server architecture.