New Delhi: Browser-based cyberattacks are becoming increasingly sophisticated, with threat actors now exploiting users’ trust in familiar web interfaces. A newly discovered malware-as-a-service (MaaS) toolkit named ‘Stanley’, identified in January 2026, has heightened concerns among cybersecurity experts due to its ability to redirect users to fraudulent websites while displaying a legitimate URL in the browser’s address bar.
A Browser Attack That Looks Legitimate
According to security researchers, the technique employed by Stanley is designed to be nearly undetectable for ordinary users. Despite visiting what appears to be a genuine website, victims unknowingly interact with a fake interface controlled by attackers. The primary objective of the toolkit is to harvest login credentials, banking details, and other sensitive financial information without raising suspicion.
Sold on Underground Forums
Stanley was first advertised on January 12, 2026, on Russian-language cybercrime forums, where it was offered by a vendor using the name “Стэнли.” Reports indicate that the toolkit is priced between $2,000 and $6,000, depending on features. Higher-tier packages reportedly include a claim of “guaranteed publication” of malicious browser extensions on the Google Chrome Web Store, a claim that has raised fresh questions about extension review mechanisms.
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The malware disguises itself as a legitimate notes and bookmarks extension called “Notely.” This social-engineering approach plays a central role in its success. Once users install the extension believing it to be harmless, it begins executing malicious activity in the background, including website spoofing and credential theft.
Precision Targeting and Persistent Control
Researchers from cybersecurity firm Varonis, who analyzed the toolkit’s technical framework and distribution model, said Stanley operates through a web-based control panel that allows attackers to configure campaigns for specific victims. Using this dashboard, threat actors can define precise website hijacking rules based on user behavior.
In a typical attack scenario, the operator selects a “source URL” — the legitimate website the user intends to visit — and a corresponding “target URL,” which hosts the phishing content. When the victim accesses the real site, the malicious extension instantly overlays a full-screen iframe containing the fake page. Crucially, the browser continues to display the authentic domain name, giving users little reason to suspect foul play.
Stanley’s infection mechanism relies heavily on extensive browser extension permissions, granting it near-complete visibility into browsing activity. Once installed, the malicious code executes at the earliest stage of page loading, before legitimate website content becomes visible to the user.
The toolkit assigns each victim a unique identifier based on their IP address, enabling attackers to selectively target individuals and track the same user across multiple browsers or devices. Researchers noted that the extension communicates with its command-and-control servers every ten seconds to receive updated instructions.
Another notable feature is Stanley’s domain rotation capability, which ensures operational continuity. If one command server or domain is taken offline, the extension automatically switches to a backup domain, allowing the attack to persist without interruption.
A Marketplace Blind Spot
Varonis researchers estimate that thousands of users have already been targeted using the Stanley toolkit. The attacker control panel reportedly displays detailed victim information, including IP addresses, online status, and recent activity logs, providing threat actors with real-time visibility into compromised systems.
Cybersecurity experts warn that the case highlights systemic vulnerabilities in browser extension marketplaces. While extensions undergo scrutiny during initial approval, post-publication updates often receive limited monitoring, creating opportunities for malicious code to be introduced later.
Enterprises have been advised to adopt strict extension allow-listing policies and restrict installation to vetted tools only. Individual users, meanwhile, are being urged to limit the number of browser extensions they install and carefully review permission requests before granting access.
Experts say the emergence of toolkits like Stanley underscores a broader shift in the cybercrime landscape, with browsers increasingly becoming a primary battleground for digital fraud and data theft.
