H3 is a minimal H(TTP) framework. In versions 2.0.0-0 through 2.0.1-rc.16, the "mount()" method in h3 uses a simple "startsWith()" check to determine whether incoming requests fall under a mounted sub-application's path prefix. Because this check does not verify a path segment boundary (i.e., that the next character after the base is "/" or end-of-string), middleware registered on a mount like "/admin" will also execute for unrelated routes such as "/admin-public", "/administrator", or "/adminstuff". This allows an attacker to trigger context-setting middleware on paths it was never intended to cover, potentially polluting request context with unintended privilege flags. Version 2.0.2-rc.17 contains a patch.