CVE-2026-75833 Grav API Plugin Open Redirect via Backslash Bypass
Attackers can redirect authenticated users to malicious sites via a backslash bypass in the Grav API plugin's OAuth return URL validation.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-75833?
CVE-2026-75833 is a high-severity vulnerability in getgrav grav, published on 18 Aug 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Official description
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.
Weakness: CWE-601
Which versions are affected by CVE-2026-75833?
How do I fix CVE-2026-75833?
No fix has been published for CVE-2026-75833 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-75833 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-75833 exists.
Sources
Also known as GHSA-chr5-7vjc-3p97.