[Webkit-unassigned] [Bug 237912] New: STP 141: instanceof value wrong in MutationObserver callback for Safari extensions
bugzilla-daemon at webkit.org
bugzilla-daemon at webkit.org
Tue Mar 15 11:42:12 PDT 2022
https://bugs.webkit.org/show_bug.cgi?id=237912
Bug ID: 237912
Summary: STP 141: instanceof value wrong in MutationObserver
callback for Safari extensions
Product: WebKit
Version: Safari Technology Preview
Hardware: Mac (Intel)
OS: macOS 11
Status: NEW
Severity: Blocker
Priority: P2
Component: New Bugs
Assignee: webkit-unassigned at lists.webkit.org
Reporter: opendarwin at lapcatsoftware.com
Created attachment 454735
--> https://bugs.webkit.org/attachment.cgi?id=454735&action=review
Sample Xcode project
This bug occurs with Safari Technology Release 141 (Safari 15.4, WebKit 16614.1.3.7) on macOS 11.6.5. The bug does not occur with Safari 15.3 or Safari 15.4 (released yesterday), only with Safari Technology Preview.
The bug is that JavaScript instanceof is returning false when it should return true in the callback of MutationObserver for Safari extensions, both Safari web extensions and Safari app extensions. This bug does not seem to affect scripts in the web pages, only extension scripts.
Attached is a sample Safari web extension Xcode project that demonstrates the bug. Just enable the extension, run it on any web site, such as cnn.com, and look at the console log. For HTML <div> elements, it should log true true for instanceof HTMLElement and instanceof HTMLDivElement, but it logs false false in Safari Technology Preview 141.
This bug is a massive problem for me, a showstopper for several of my Safari extensions in the App Store. It totally breaks essential functionality in my extensions.
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