thisArg.collectedHeaders is undefined

[piquark6046]

After aagag.com#%#//scriptlet('prevent-xhr', 'pagead2.googlesyndication.com/pagead/js/adsbygoogle.js') in AdGuard Browser Extension on Firefox, an Uncaught TypeError: can't access property "length", thisArg.collectedHeaders is undefined error is raised.

Scriptlets/src/scriptlets/prevent-xhr.js

Lines 248 to 262 in 5c1ccff

	const getHeaderWrapper = (target, thisArg, args) => {
	if (!thisArg.collectedHeaders.length) {
	return null;
	}
	// The search for the header name is case-insensitive
	// https://developer.mozilla.org/en-US/docs/Web/API/XMLHttpRequest/getResponseHeader
	const searchHeaderName = args[0].toLowerCase();
	const matchedHeader = thisArg.collectedHeaders.find((header) => {
	const headerName = header[0].toLowerCase();
	return headerName === searchHeaderName;
	});
	return matchedHeader
	? matchedHeader[1]
	: null;
	};

Instead of simply using logical not operator (!), please use typeof operator to test before it.

Environment

• Operating System: Ubuntu 23.04
• Browser: Mozilla Firefox Developer Edition 117.0b2
• AdGuard Browser Extension version: 4.2.142
• URL: https://aagag.com/issue/?idx=1267082

[piquark6046]

AdGuard Browser Extension 4.1.57 on Firefox is not affected.

[AdamWr]

I suppose that it might be the same issue as here - #347 (comment)

[piquark6046]

I think that this issue has to be prioritized to a upper class because this issue causes breakages if prevent-xhr scriptlet is applied in a webpage.
Confirmed a website having this issue:

• https://laftel.net
• www.channel4.com AdguardFilters#158932

[AdamWr]

It should be already fixed in scriptlets library version 1.9.62.
The latest scriptlets library (1.9.62) is already in AdGuard AdBlocker extension 4.2.151 and as far as I can see, it works correctly on these websites.