Disavowed: Chrome plans to deprecate ‘document.domain’ lays the groundwork for shift in browser security

John Leyden

26 April 2022 at 17:30 UTC

Updated: 26 April 2022 at 18:54 UTC

Making doc.area immutable

Web builders who depend on a workaround that relaxed the identical origin coverage to permit subdomains to change content material will quickly want to take a unique strategy.

Starting with the upcoming Chrome 106 launch, Google’s internet browser will shut a loophole that went towards finest practices in addition to, extra importantly, posing a hazard in hosted environments.

More particularly, ranging from Chrome 106, web sites can be unable to set ‘doc.area’, a way that enables same-site-but-cross-origin communications.

Read more of the latest news about browser security

The present mainstream launch of Google’s browser – Chrome 100 – already throws up a warning about the soon-to-be deprecated facility that enables web site builders to reap the benefits of doc.area to loosen up the same-origin coverage.

Website builders are urged to scan their web site to entry the potential influence of the deprecation of doc.area earlier than swamping out cases the place the ‘hack’ has been utilized for a safer methodology of cross-origin communication, as defined in a latest blog post by Google.

“On Chrome, web sites can be unable to set doc.area. You will want to use different approaches, equivalent to postMessage() or the Channel Messaging API, to talk cross-origin,” Google explains.

“If your web site depends on same-origin coverage rest through doc.area to perform accurately, the website will want to ship an Origin-Agent-Cluster: ?0 header, as will all different paperwork that require that conduct.”

These different strategies have existed for some years. However in actuality, few builders depend on doc.area to loosen up the same-origin coverage.


Google is successfully killing a function that’s not broadly used and is gaining an enormous security profit consequently.

The improvement switches the browser security paradigm from site isolation to origin isolation – drastically lowering the utility of Spectre-style attacks in the course of.

Google and different browser makers are laying the groundwork for stopping attackers from pivoting between subdomains utilizing Spectre-style assaults.

The same-origin policy provides assurances that any internet web page can’t entry (modify, or extract information from) one other web page, until these pages are hosted on the identical origin.

The use of doc.area by internet devs runs opposite to this rubric and poses a specific risk in the context of Spectre-style assaults, as a Github post by Google Chrome security developer Mike West illustrates.

Host of issues

Websites set doc.area in order to permit same-site paperwork to talk extra simply. Whilst providing comfort advantages, the strategy introduces a security threat, as Google explains:

If a internet hosting service supplies totally different subdomains per person, an attacker can set doc.area to fake they’re the same-origin as one other person’s web page.

Further, an attacker can host a web site underneath a shared internet hosting service, which serves websites via the identical IP handle with totally different port numbers.

In that case, the attacker can fake to be on the same-site-but-same-origin as yours. This is feasible as a result of doc.area ignores the port quantity a part of the area.

Other browser makers, including Mozilla, are additionally trying to deprecate doc.area.

RELATED Spectre attacks against websites still a serious threat, Google warns


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