5 Common Vulnerabilities Found in Every Web App Pentest

After running dozens of web application penetration tests, the same handful of issues keep showing up — regardless of industry or tech stack.

Broken access control tops the list. APIs that don't properly verify a user's permission before returning data are everywhere, especially in apps built quickly without a security review.

Second is misconfigured authentication — weak password policies, missing account lockouts, and session tokens that don't expire.

Third, sensitive data exposure: API responses that leak more fields than the frontend actually uses, often including internal IDs or other users' data.

Fourth, outdated dependencies. A single unpatched library can open the door to a known exploit, even in an otherwise well-built application.

Fifth, insufficient logging — when we ask 'how would you know if this had already happened,' the honest answer is often 'we wouldn't.'

None of these require exotic attacks to fix. They require a testing process that treats security as part of the build, not an afterthought.