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🤖 HackTricks / DOM Invader

DOM Invader

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DOM Invader

DOM Invader is a browser tool installed in Burp Suite's built-in Chromium browser. It assists in detecting DOM XSS and other client-side vulnerabilities (prototype pollution, DOM clobbering, etc.) by automatically instrumenting JavaScript sources and sinks. The extension ships with Burp and only needs to be enabled.

DOM Invader adds a tab to the browser’s DevTools panel that lets you:

  1. Identify controllable sinks in real time, including context (attribute, HTML, URL, JS) and applied sanitization.
  2. Log, edit and resend postMessage() web-messages, or let the extension mutate them automatically.
  3. Detect client-side prototype-pollution sources and scan for gadget→sink chains, generating PoCs on-the-fly.
  4. Find DOM clobbering vectors (e.g. id / name collisions that overwrite global variables).
  5. Fine-tune behaviour via a rich Settings UI (custom canary, auto-injection, redirect blocking, source/sink lists, etc.).

1. Enable it

  1. Open Proxy ➜ Intercept ➜ Open Browser (Burp’s embedded browser).
  2. Click the Burp Suite logo (top-right). If it’s hidden, click the jigsaw-piece first.
  3. In DOM Invader tab, toggle Enable DOM Invader ON and press Reload.
  4. Open DevTools ( F12 / Right-click ➜ Inspect ) and dock it. A new DOM Invader panel appears.

Burp remembers the state per profile. Disable it under Settings ➜ Tools ➜ Burp’s browser ➜ Store settings... if required.

2. Inject a Canary

A canary is a random marker string (e.g. xh9XKYlV) that DOM Invader tracks. You can:

  • Copy it and manually inject it in parameters, forms, Web-Socket frames, web-messages, etc.
  • Use Inject URL params / Inject forms buttons to open a new tab where the canary is appended to every query key/value or form field automatically.
  • Search for an empty canary to reveal all sinks regardless of exploitability (great for reconnaissance).

Custom canary (2025+)

Burp 2024.12 introduced Canary settings (Burp-logo ➜ DOM Invader ➜ Canary). You can:

  • Randomize or set a custom string (helpful for multi-tab testing or when the default value appears naturally on the page).
  • Copy the value to clipboard.
  • Changes require Reload.

3. Web-messages (postMessage)

The Messages sub-tab records every window.postMessage() call, showing origin, source, and data usage.

• Modify & resend: double-click a message, edit data, and press Send (Burp Repeater-like).

• Auto-fuzz: enable Postmessage interception ➜ Auto-mutate in settings to let DOM Invader generate canary-based payloads and replay them to the handler.

Field meaning recap:

  • origin – whether the handler validates event.origin.
  • data – payload location. If unused, the sink is irrelevant.
  • source – iframe / window reference validation; often weaker than strict‐origin checking.

4. Prototype Pollution

Enable under Settings ➜ Attack types ➜ Prototype pollution.

Workflow:

  1. Browse – DOM Invader flags pollution sources (__proto__, constructor, prototype) found in URL/query/hash or JSON web-messages.
  2. Test – clicks Test to open a PoC tab where Object.prototype.testproperty should exist:

let obj = {};
console.log(obj.testproperty); // ➜ 'DOM_INVADER_PP_POC'

3. Scan for gadgets – DOM Invader bruteforces property names and tracks whether any end up in dangerous sinks (e.g. innerHTML).
4. Exploit – when a gadget-sink chain is found an Exploit button appears that chains source + gadget + sink to trigger alert.

Advanced settings (cog icon):

  • Remove CSP / X-Frame-Options to keep iframes workable during gadget scanning.
  • Scan techniques in separate frames to avoid __proto__ vs constructor interference.
  • Disable techniques individually for fragile apps.

5. DOM Clobbering

Toggle Attack types ➜ DOM clobbering. DOM Invader monitors dynamically created elements whose id/name attributes collide with global variables or form objects (<input name="location"> → clobbers window.location). An entry is produced whenever user-controlled markup leads to variable replacement.

6. Settings Overview (2025)

DOM Invader is now split into Main / Attack Types / Misc / Canary categories.

  1. Main
  2. Enable DOM Invader – global switch.
  3. Postmessage interception – turn on/off message logging; sub-toggles for auto-mutation.

  4. Custom Sources/Sinks – cog icon ➜ enable/disable specific sinks (e.g. eval, setAttribute) that may break the app.

  5. Attack Types

  6. Prototype pollution (with per-technique settings).

  7. DOM clobbering.

  8. Misc

  9. Redirect prevention – block client-side redirects so the sink list isn’t lost.
  10. Breakpoint before redirect – pause JS just before redirect for call-stack inspection.

  11. Inject canary into all sources – auto-inject canary everywhere; configurable source/parameter allow-list.

  12. Canary

  13. View / randomize / set custom canary; copy to clipboard. Changes require browser reload.

7. Tips & Good Practices

  • Use distinct canary – avoid common strings like test, otherwise false-positives occur.
  • Disable heavy sinks (eval, innerHTML) temporarily if they break page functionality during navigation.
  • Combine with Burp Repeater & Proxy – replicate the browser request/response that produced a vulnerable state and craft final exploit URLs.
  • Remember frame scope – sources/sinks are displayed per browsing context; vulnerabilities inside iframes might need manual focus.
  • Export evidence – right-click the DOM Invader panel ➜ Save screenshot to include in reports.

References

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