[BUG] `GM_addElement` return null, when parent_node is not in document.

[F9y4ng]

Actual Behavior

GM_addElement return null, when parent_node is not in document.

GM_addElement(Node in ShadowRoot, "img", { id: "test1", src: "abc.jpg" })
GM_addElement(Node in iframe, "img", { id: "test2", src: "abc.jpg" })

The IMG element will be inserted normally, but the element id attribute will be reset to default and the return value will be null instead of the successfully inserted element object.

Expected Behavior

When parent_node is not in document, the custom attributes can be written normally and the return value is correct.

Additional context

• Similar issue, as I mentioned in [Bug] GM_addElement report TypeError: Illegal invocation when inserting an element from parent into a same-origin frame #2313.
• These operations are normal in Violentmonkey, but are problematic in all versions of Tampermokey.

[derjanb]

Should be fixed at 5.5.6236 (crx|xpi in review)

Chrome/Edge users, please download the crx file linked above and drag and drop it to the extensions page chrome://extensions or wait for the Chrome Web Store review being done.
Firefox users please wait for the XPI being reviewed and install the BETA version or check for BETA version updates at about:addons once the review is finished.

For a quick fix please export your settings and scripts as zip or (JSON) file at the "Utilities" tab and import it back at the fixed BETA version.

[F9y4ng]

Hi， @derjanb

GM_addElement(Node in ShadowRoot, "img", { id: "test1", src: "abc.jpg" })
GM_addElement(Node in iframe, "img", { id: "test2", src: "abc.jpg" })

5.5.6236 has fixed the problem in the above situation, and my test is normal.

But, GM_addElement(null, "img", { id: "test1", src: "abc.jpg" }) return null, and console report VM9171:10 injected: addElement: failed to find created element, and the IMG element already inserted normally.

However, GM_addElement(void 0, "img", { id: "test1", src: "abc.jpg" }) return the inserted element object normally, and the IMG element already inserted normally.

In my opinion, when parent_node is null, should the element NOT be inserted and return null directly to distinguish that when parent_node is undefined, it will be inserted into the current document by default? Anyway, I think the error message shouldn't appear when parent_node is null.

[derjanb]

and console report VM9171:10 injected: addElement: failed to find created element

This is working fine here. Both calls return the img element.

// ==UserScript==
// @name         GM_addElement null
// @namespace    http://tampermonkey.net/
// @version      2026-04-07-10-02-36
// @description  try to take over the world!
// @author       You
// @match        https://example.com/*
// @icon         data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==
// @grant        GM_addElement
// ==/UserScript==

const a = GM_addElement(null, "img", { id: "test1", src: "abc.jpg" });
const b = GM_addElement(void 0, "img", { id: "test1", src: "abc.jpg" });

console.log('#', a, b);

[F9y4ng]

What I mean is that when parent_node is null, it should return null directly, and without inserting IMG. Because if I want to insert an IMG in an element in ShadowRoot, but it doesn't get that element properly (it returns null), the IMG will be inserted into the current document instead of the node in ShadowRoot, which is a unintended error.

When parent_node is undefined, you can insert the current document at will, which is the same as when you do not fill in the parent_node.

I think these two should be different.