An open redirect vulnerability exists in the return_page redirection functionality of phpGACL 3.3.7, OpenEMR 5.0.2 and OpenEMR development version 6.0.0 (commit babec93f600ff1394f91ccd512bcad85832eb6ce). A specially crafted HTTP request can redirect users to an arbitrary URL. An attacker can provide a crafted URL to trigger this vulnerability.