🛡️ Security Lab Track A · Web Application Security · Stage 0

Track A · Stage 0

Web Application Security

Cookie & localStorage Tampering easynot started

A members portal decides admin access entirely in the browser. Read the flag that only an admin with debug mode enabled can see, using DevTools (view source, cookies, local storage).

1. DevTools → Application → Cookies: set role=admin for this origin. Why: the page reads your access level from a browser-stored cookie you control; the server never verifies it.

2. DevTools → Application → Local Storage: add debug = 1. The HTML comment ZGVidWcgPSAx... base64-decodes to debug = 1. Why: client-side feature flags are just data in your browser.

3. Reload — both checks pass and the flag appears.

Lesson: never trust client-controlled values for authorization.