SSRF (server-side request forgery)

Tricking your server into fetching a URL the attacker chose, often an internal address the attacker cannot reach directly.

Any feature that fetches a user-supplied URL can be abused: link previews, image imports, webhooks, PDF rendering, AI agents with a browsing tool. The attacker points it at internal services or cloud metadata endpoints that hand out credentials. Blocking “localhost” is not enough, because redirects and DNS can lead to the same place.

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Related terms

RCE (remote code execution): A vulnerability that lets an attacker run their own code on your server or device over the network.
Webhook: An HTTP request one system sends to another when something happens, instead of the other system asking repeatedly.
OWASP Top 10: The OWASP Foundation’s list of the ten most critical web application security risks, updated every few years.

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