Snyk warns AI coding agents keep shipping broken access control

AI coding agents are repeatedly producing broken access control — authorisation code that fails to stop one user reading another user's data — according to a blog post published by the security vendor Snyk on 1 October 2026.

Snyk's argument is that this class of defect is unusually well suited to slipping past the controls teams already have. The company says agent-written authorisation logic can compile, run and pass human code review while still exposing one tenant's data to another. In other words, nothing visibly breaks. The feature works, the tests go green, and the reviewer sees plausible code. The failure only shows up when the wrong person asks for the wrong record.

That is what makes broken access control hard to detect, Snyk says. Most automated checks look for patterns: a dangerous function, an unsanitised input, a known vulnerable dependency. Access control is different because correctness depends on intent. A scanner cannot tell whether a given database query was supposed to be scoped to the current organisation, because the rule lives in the product's requirements rather than in the code itself. A missing filter on a query looks identical to a query that was never meant to be filtered.

The multi-tenancy angle is the sharpest part of Snyk's warning. In a multi-tenant application — one codebase and one database serving many separate customers — a single missing ownership check can turn an ordinary endpoint into a cross-customer data leak. The blast radius is not one user's account but, potentially, every account on the platform.

Snyk frames the problem as a reason to change where teams put their effort rather than a reason to stop using coding agents. The post is pitched at prevention: understanding why the defect recurs, and building guardrails that assume agent output will contain authorisation gaps rather than hoping review will catch them.

The practical takeaway for teams running coding agents is uncomfortable. Code review, the control most organisations lean on hardest when they adopt AI-generated code, is precisely the control Snyk says this bug class defeats. A reviewer reading a diff has limited context about which records a given user is entitled to see, and the agent's code will usually look reasonable in isolation.

Snyk is a commercial supplier of application security tooling, and the post sits within its own product area, so the framing should be read with that in mind. The underlying observation — that authorisation correctness cannot be inferred from the code alone — is not specific to any one vendor's tooling, and it applies equally to human-written code. What changes with agents is volume. More code, generated faster, with less context per change, means more opportunities for a missing ownership check to reach production unnoticed.