The global `browser` can be overriden by DOM elements

[ouuan]

The issue fixed in #153 was introduced again in #582. Now the browser global can be overriden by a DOM element if there is either browser.runtime.id or exports:

webextension-polyfill/src/browser-polyfill.js

Line 13 in 6a42cbe

if (!(globalThis.browser && globalThis.browser.runtime && globalThis.browser.runtime.id)) {

<form id="browser"></form>
<form id="browser" name="runtime"></form>

webextension-polyfill/scripts/babel-transform-to-umd-module.js

Line 7 in 6a42cbe

} else if (typeof exports !== "undefined") {

<form id="exports">

This can be fixed by checking that browser.runtime.id and exports are of the correct type, e.g. are not instances of HTMLElement or HTMLCollection.

Credit: discovered by me and skadi.