We are upgrading our microservices and want to secure our data endpoints. How do hackers exploit APIs when is left unaddressed? I want to understand how attackers manipulate API requests to access unauthorized user records so we can patch these gaps.
3 answers
Hackers routinely exploit APIs by targeting broken object level authorization, commonly known as BOLA or IDOR. In a typical scenario, an attacker intercepts the API traffic using tools like Burp Suite to analyze the structure of the HTTP requests. If the API relies on sequential or predictable identifiers within the URL path, headers, or JSON body—such as /api/v1/user/1001—the hacker simply alters that ID to 1002. If the backend server fails to validate whether the logged-in user actually owns or has permission to view record 1002, it will return the sensitive data.
This makes total sense for standard GET requests, but how do hackers exploit APIs using this vulnerability during POST or PUT requests? Are they altering the payload data or focusing on the headers?
Attackers exploit this by fuzzing user IDs in API requests, looking for backend systems that check authentication but completely forget to enforce proper authorization policies.
Exactly, Megan. Automated tools make it incredibly easy for bad actors to rotate thousands of sequential IDs in seconds, mapping out unprotected endpoints rapidly.
When targeting POST or PUT endpoints, hackers manipulate object IDs embedded inside the JSON payload rather than the URL. For example, they might change a tenant_id or account_id parameter inside the request body to force the server to update records belonging to a completely different user or organization, bypassing client-side UI restrictions entirely.