EasyAdmin custom-action dispatcher bypasses access_control on other routes

EasyAdmin is a fast and modern admin generator for Symfony applications. From 4.0.0 until 4.29.16 and 5.5.1, EasyAdmin serves all backend requests through a single dashboard route and, for custom actions (Action::linkToRoute() and MenuItem::linkToRoute()), swaps the executed controller based on the routeName query parameter on the kernel.controller event. The swap happens after Symfony's security firewall has already evaluated access_control against the original dashboard URL, and the routeName value was not validated. As a result, a path-based access_control rule protecting the target route was never evaluated, so a low-privilege backend user who can reach a single EasyAdmin URL and knows a target route's name can execute that route's controller, bypassing the path-based rule. Only path-based protections are bypassed. Routes whose controller enforces its own authorization with #[IsGranted] or denyAccessUnlessGranted() remain protected because those checks are recomputed against the swapped-in controller. This issue is fixed in versions 4.29.16 and 5.5.1.

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