Catalog/VULNERABILITY/browser-storage
SCAN-ID: BROWSER-STORAGEREVISION 2026.4
VULNERABILITYCVSS 6.2 (MEDIUM)

Client-Side Browser Storage Leak Scanner

Detect sensitive tokens, passwords, or PII stored in unencrypted localStorage or sessionStorage.

Technical Scope & Verification Behavior

Parses client bundles to detect storage of access_token, user credentials, or unmasked credit card details in browser web storage.

Automated Inspection Checks (6)
Passive URL parameter fuzzing
Non-destructive boundary tests
Header & cookie flag assertions
Differential latency timing

Proof of Concept (PoC) Vector

Canonical test payload dispatched during security surface audits.

localStorage.setItem('auth_token', jwt)

Probe Execution Simulator

Watch the probe engine test this signature in an isolated sandbox.

probe-runner (isolated ephemeral container)
Click 'Simulate Check' to watch the headless audit engine test this vector.

Remediation Patch

HttpOnly Cookie Storage

patch.diff (typescript)
--- a/handler.typescript (Vulnerable)
localStorage.setItem('session_token', token);
+++ b/handler.typescript (Remediated)
cookies().set('session_token', token, { httpOnly: true, secure: true, sameSite: 'lax' });

Store session tokens in HttpOnly cookies so they cannot be accessed or extracted via JavaScript XSS attacks.

AI Agent Prompt (Cursor · Claude · Copilot)

Copy and paste into your editor to refactor this issue automatically.

"Refactor client authentication flow to store session tokens in HttpOnly, Secure cookies instead of browser localStorage."

Run Isolated Check

Test your public domain specifically for Client-Side Browser Storage Leak Scanner.

100% passive • No server load

Specification Details

CVSS Score
6.2 / 10.0
Severity Level
MEDIUM
Category
VULNERABILITY
Test Vectors
6 automated
Execution SLA
< 2.5 seconds
False Positive Defense
Strict assertion
Related Standards
#Storage#localStorage#Cookies#PII

Run continuous monitoring for Client-Side Browser Storage Leak Scanner

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