The Photo Gallery, Sliders, Proofing and Themes – NextGEN Gallery plugin for WordPress is vulnerable to Remote Code Execution in all versions up to, and including, 4.4.1 via the legacy_render function. This is due to broken authorization on the Lightroom gallery_edit endpoint combined with mass assignment of gallery path and unrestricted file upload into a registered template directory, whose extension check uses a substring match that accepts sanitized .php_ filenames as valid templates. This makes it possible for authenticated attackers, with custom-level access and above, to execute code on the server. Exploitation requires the authenticated attacker to be the stored author of at least one existing NextGEN gallery, as ownership of that gallery is the sole authorization check gating the mass-assignment and upload steps.