In 2022, we dived deep into an attack method called browser-in-the-browser — originally developed by the cybersecurity researcher known as mr.d0x. Back then, no actual examples existed of this model being used in the wild. Fast-forward four years, and browser-in-the-browser attacks have graduated from the theoretical to the real: attackers are now using them in the field. In this post, we revisit what exactly a browser-in-the-browser attack is, show how hackers are deploying it, and, most importantly, explain how to keep yourself from becoming its next victim.
For starters, let’s refresh our memories on what mr.d0x actually cooked up. The core of the attack stems from his observation of just how advanced modern web development tools — HTML, CSS, JavaScript, and the like — have become. It’s this realization that inspired the researcher to come up with a particularly elaborate phishing model.
A browser-in-the-browser attack is a sophisticated form of phishing that uses web design to craft fraudulent websites imitating login windows for well-known services like Microsoft, Google, Facebook, or Apple that look just like the real thing. The researcher’s concept involves an attacker building a legitimate-looking site to lure in victims. Once there, users can’t leave comments or make purchases unless they “sign in” first.
Signing in seems easy enough: just click the Sign in with {popular service name} button. And this is where things get interesting: instead of a genuine authentication page provided by the legitimate service, the user gets a fake form rendered inside the malicious site, looking exactly like… a browser pop-up. Furthermore, the address bar in the pop-up, also rendered by the attackers, displays a perfectly legitimate URL. Even a close inspection won’t reveal the trick.
From there, the unsuspecting user enters their credentials for Microsoft, Google, Facebook, or Apple into this rendered window, and those details go straight to the cybercriminals. For a while this scheme remained a theoretical experiment by the security researcher. Now — real-world attackers have added it to their arsenals.
Attackers have put their own spin on mr.d0x’s original concept: recent browser-in-the-browser hits have been kicking off with emails designed to alarm recipients. For instance, one phishing campaign posed as a law firm informing the user they’d committed a copyright violation by posting something on Facebook. The message included a credible-looking link allegedly to the offending post.
Attackers sent messages on behalf of a fake law firm alleging copyright infringement — complete with a link supposedly to the problematic Facebook post. Source
Interestingly, to lower the victim’s guard, clicking the link didn’t immediately open a fake Facebook login page. Instead, they were first greeted by a bogus Meta CAPTCHA. Only after passing it was the victim presented with the fake authentication pop-up.
This isn’t a real browser pop-up; it’s a website element mimicking a Facebook login page — a ruse that allows attackers to display a perfectly convincing address. Source
Naturally, the fake Facebook login page followed mr.d0x’s blueprint: it was built entirely with web design tools to harvest the victim’s credentials. Meanwhile, the URL displayed in the forged address bar pointed to the real Facebook site — www.facebook.com.
The fact that scammers are now deploying browser-in-the-browser attacks just goes to show that their bag of tricks is constantly evolving. But don’t despair — there’s a way to tell if a login window is legit. A password manager is your friend here, which, among other things, acts as a reliable security litmus test for any website.
That’s because when it comes to auto-filling credentials, a password manager looks at the actual URL, not what the address bar appears to show, or what the page itself looks like. Unlike a human user, a password manager can’t be fooled with browser-in-the-browser tactics, or any other tricks, like domains having a slightly different address (typosquatting) or phishing forms buried in ads and pop-ups. There’s a simple rule: if your password manager offers to auto-fill your login and password, you’re on a website you’ve previously saved credentials for. If it stays silent, something’s fishy.
Beyond that, following our time-tested advice will help you defend against various phishing methods, or at least minimize the fallout if an attack succeeds:
Finally, this post serves as yet another reminder that theoretical attacks described by cybersecurity researchers often find their way out into the wild. So, keep an eye on our blog, and subscribe to our Telegram channel to stay up to speed on the latest threats to your digital security and how to shut them down.
Read about other inventive phishing techniques scammers are using day in day out:
In November 2025, Kaspersky experts uncovered a new stealer named Stealka, which targets Windows users’ data. Attackers are using Stealka to hijack accounts, steal cryptocurrency, and install a crypto miner on their victims’ devices. Most frequently, this infostealer disguises itself as game cracks, cheats and mods.
Here’s how the attackers are spreading the stealer, and how you can protect yourself.
A stealer is a type of malware that collects confidential information stored on the victim’s device and sends it to the attackers’ server. Stealka is primarily distributed via popular platforms like GitHub, SourceForge, Softpedia, sites.google.com, and others, disguised as cracks for popular software, or cheats and mods for games. For the malware to be activated, the user must run the file manually.
Here’s an example: a malicious Roblox mod published on SourceForge.
Attackers exploited SourceForge, a legitimate website, to upload a mod containing Stealka
And here’s one on GitHub posing as a crack for Microsoft Visio.
A pirated version of Microsoft Visio containing the stealer, hosted on GitHub
Sometimes, however, attackers go a step further (and possibly use AI tools) to create entire fake websites that look quite professional. Without the help of a robust antivirus, the average user is unlikely to realize anything is amiss.
A fake website pretending to offer Roblox scripts
Admittedly, the cracks and software advertised on these fake sites can sometimes look a bit off. For example, here the attackers are offering a download for Half-Life 3, while at the same time claiming it’s not actually a game but some kind of “professional software solution designed for Windows”.
Malware disguised as Half-Life 3, which is also somehow “a professional software solution designed for Windows”. A lot of professionals clearly spent their best years on this software…
The truth is that both the page title and the filename are just bait. The attackers simply use popular search terms to lure users into downloading the malware. The actual file content has nothing to do with what’s advertised — inside, it’s always the same infostealer.
The site also claimed that all hosted files were scanned for viruses. When the user decides to download, say, a pirated game, the site displays a banner saying the file is being scanned by various antivirus engines. Of course, no such scanning actually takes place; the attackers are merely trying to create an illusion of trustworthiness.
The pirated file pretends to be scanned by a dozen antivirus tools
Stealka has a fairly extensive arsenal of capabilities, but its prime target is data from browsers built on the Chromium and Gecko engines. This puts over a hundred different browsers at risk, including popular ones like Chrome, Firefox, Opera, Yandex Browser, Edge, Brave, as well as many, many others.
Browsers store a huge amount of sensitive information, which attackers use to hijack accounts and continue their attacks. The main targets are autofill data, such as sign-in credentials, addresses, and payment card details. We’ve warned repeatedly that saving passwords in your browser is risky — attackers can extract them in seconds. Cookies and session tokens are perhaps even more valuable to hackers, as they can allow criminals to bypass two-factor authentication and hijack accounts without entering the password.
The story doesn’t end with the account hack. Attackers use these compromised accounts to spread the malware further. For example, we discovered the stealer in a GTAV mod posted on a dedicated site by an account that had previously been compromised.
Beyond stealing browser data, Stealka also targets the settings and databases of 115 browser extensions for crypto wallets, password managers, and 2FA services. Here are some of the most popular extensions now at risk:
Finally, the stealer also downloads local settings, account data, and service files from a wide variety of applications:
That’s an extensive list — and we haven’t even named all of them! In addition to local files, this infostealer also harvests general system data: a list of installed programs, the OS version and language, username, computer hardware information, and miscellaneous settings. And as if that weren’t enough, the malware also takes screenshots.
Curious what other stealers are out there, and what they’re capable of? Read more in our other posts:
Brian King // Do you know what that browser plugin is doing? There’s a browser plugin for just about everything. You can find one to change the name of […]
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