How do you mitigate open redirect in login returnUrl?
PICTURE THIS: DOM IS A TREE
Simple meaning
Only local URLs or an allowlist of domains.
WHY — Security instead of guessing?
Why interviewers care about Security:
question about Security.
trade-offs, and what you would actually do on a .NET MVC project - not buzzwords.
Name the idea, why it exists, then one short example.
End with when you use it and one common pitfall.
STEPS — What happens step by step?
Before you speak the answer, walk the interviewer through these steps:
- 1Only local URLs or
an allowlist of domains.
- 2Why it exists
I use Url.IsLocalUrl before Redirect.
- 3Attackers otherwise phish with
a trusted login page.
- 4Give an example
One tiny concrete case you can say aloud.
- 5Common mistake
What juniors usually get wrong.
- 6Close
When you pick this over the alternative.
EXAMPLE — See it in action
Here's a short line you can speak, broken into clear beats:
Note: Adapt this scaffold to your own project — keep it under 60–90 seconds.
Key takeaway
Only local URLs or an allowlist of domains. I use Url.IsLocalUrl before Redirect.