Open redirect testing
An open redirect is when your app takes a URL from a request and sends the user there without checking it — letting an attacker use your trusted domain as a springboard to a malicious site. On its own it's often rated low, but it powers convincing phishing and, chained into OAuth, real token theft. Sintropyc finds every redirect parameter and proves which actually send users off-site.
Why a 'low' bug is worth testing
The link looks like yours — yourapp.com/login?next=… — so a victim trusts it, then lands on the attacker's page. The real damage comes from chaining:
- Phishing — a genuine link on your domain that ends on a fake login
- OAuth / OIDC token theft — a redirect that leaks an auth code or token to an attacker-controlled URL
- Filter and SSRF bypass — a redirect used to slip past allowlists or reach internal targets
- Credential relay — chaining the redirect into a broader account-takeover flow
Where open redirects hide
Anywhere your app remembers 'where to send you next': ?next=, ?returnUrl=, ?redirect=, login and logout flows, OAuth redirect_uri handling, and link-tracking or preview endpoints.
An open redirect is one of the cleanest findings to verify: either the app sends the user to an external host or it doesn't. Sintropyc confirms the actual off-site redirect rather than flagging the parameter alone.
How Sintropyc tests it
Sintropyc is an autonomous AI penetration testing agent. It signs in as real users across different roles, drives your product the way a customer would, and proves every finding with a working exploit — never a scanner guess. Each finding is checked by a human before it reaches you, comes with the exact fix, and is attacked again after you ship it to confirm it held.
For open redirects, Sintropyc finds redirect-taking parameters and flows, tries a controlled external destination through each (including common bypass encodings), and confirms whether the app actually issues an off-site redirect. Where it can extend into an OAuth or auth chain, it attributes the full impact — the redirect and what it enabled.
What you get
- Every redirect parameter and auth flow tested
- Proven off-site redirects, with the bypass techniques that worked
- OAuth / token-theft chains attributed end to end where reachable
- The fix (allowlist of relative / known destinations) and a retest
Common questions
Isn't open redirect too low-severity to bother?
Alone, often yes. Chained into OAuth or phishing it becomes serious — which is exactly what Sintropyc checks. Severity reflects what was actually reachable, not the label.
What's the correct fix?
Don't redirect to raw user input. Allow only relative paths or an allowlist of known destinations, and validate on the server. Sintropyc gives the specific parameter and fix.
Do you test OAuth redirect_uri handling?
Yes — loose redirect_uri validation is a common, high-impact open-redirect chain, and it's explicitly in scope.