Libor Plucnar contributed to the shopsys/shopsys repository by enhancing backend reliability and security over a two-month period. He developed a feature to improve blog URL generation, ensuring that translations with null names are skipped, which prevents broken URLs and strengthens SEO. Using PHP and SQL within a Symfony framework, he focused on maintainable code and business value. In addition, Libor addressed a security vulnerability in the social login flow by implementing referer URL validation to prevent open redirects, renaming session constants for clarity, and enforcing strict URL acceptance, thereby improving both the security and clarity of the authentication workflow.