FOSSBilling is a free, open-source billing and client management system. Versions prior to 0.8.0 leak the exact system version through asset cache buster parameters in HTML output, bypassing the "hide_version_public" security setting. The FOSSBilling version is embedded in the query string of every "<script>" and "<link>" tag generated by the "script_tag" and "stylesheet_tag" Twig filters. This information is visible to all visitors — including unauthenticated guests — on every page, regardless of whether the "hide_version_public" setting is enabled. The "X-FOSSBilling-Version" HTTP header and the "guest.system.version" API endpoint correctly honour the "hide_version_public" setting, but the asset cache buster parameters were overlooked. Knowledge of the exact FOSSBilling version makes it significantly easier for malicious actors to identify known vulnerabilities applicable to a given installation and craft targeted exploits. While not a direct vulnerability on its own, it undermines the intended protection offered by the "hide_version_public" setting and facilitates reconnaissance. Version 0.8.0 contains a patch. There is no practical workaround that removes the version from asset URLs without modifying source code.