CVE-2026-75833

Descripción

The Grav API plugin (getgrav/grav-plugin-api, bundled with Grav 2.0-s admin-next/API stack) before version 1.0.14 contains an open redirect weakness in SsoController::sanitizeReturnTo(). The function rejects a literal -//- prefix but does not account for browsers normalizing backslashes to slashes in special (http/https) schemes, so a returnTo value such as -/\evil.com- passes the guard and is later resolved by the browser as the protocol-relative URL -//evil.com-. Following a legitimate OAuth login flow, an attacker-supplied returnTo parameter could redirect an authenticated victim to an attacker-controlled site for post-login phishing. Full browser-side exploitability depends on the admin-next SPA-s client-side oauth-callback handler and was not independently verified by the reporter.