More than 100,000 browsers have been compromised through malicious Chrome extensions in a sophisticated cybercrime operation. Security researchers identified multiple campaigns targeting users through fake AI tools, productivity extensions, and cryptocurrency utilities.
Cybersecurity platform Obsidian discovered an extension called H-Chat Assistant that siphoned OpenAI credentials from over 10,000 users. The tool, which began operations in July 2024, transmitted at least 459 unique API keys to a Telegram channel controlled by hackers before detection in January 2025.
OX Security researchers found two malicious extensions impersonating the legitimate AITOPIA extension, exfiltrating ChatGPT and DeepSeek conversations from over 900,000 Chrome downloads. One of these data-stealing extensions carried Google's "Featured" badge and remained available on the Chrome Web Store after discovery.
The attack methods vary across campaigns. Some extensions like Crypto Copilot inject hidden fees into cryptocurrency transactions, siphoning 0.05% of Solana swap amounts to attacker-controlled wallets. Others hijack affiliate links or steal authentication tokens from services like Amazon and ChatGPT.
Researchers identified at least 16 Chrome extensions sharing the same developer fingerprints, all promising AI productivity enhancements. These tools, totaling about 900 installations, were built by a single threat actor harvesting credentials and session data across multiple platforms.
The Chrome Web Store hosts over 100,000 extensions with billions of downloads recorded since launch. A Stanford University study covering July 2020 through February 2023 found that 280 million users downloaded Chrome extensions infected with malware during that period.
Extension security faces multiple challenges. The Stanford research revealed that 60% of extensions in the Chrome Web Store had never been updated, and half of known-vulnerable extensions remained available two years after disclosure.
Many malicious extensions stayed in the store for months before removal.
Attackers frequently compromise legitimate extensions by breaching developer accounts, then pushing malicious updates to existing user bases. This technique allows operations to scale rapidly while avoiding detection by conventional security software that trusts previously authorized extensions.
The primary monetization strategies include hijacking Facebook business accounts for unauthorized advertising campaigns, stealing cryptocurrency through hidden transaction fees, and harvesting API keys for credential resale. These methods generate revenue while causing financial damage to victims.
Security companies are responding to the threat. Several endpoint protection platforms have announced plans to incorporate browser extension monitoring, recognizing that security must extend to the browser layer where traditional defenses often fail.
Google's Chrome Web Store implements automated review using machine learning to detect malicious extensions, but the system faces challenges with sophisticated attacks. Researchers report that extensions can remain available for extended periods even after malicious activity is documented and reported.
The Department of Justice issued a final rule in January 2025 implementing Executive Order 14117, addressing national security risks from data transactions involving sensitive personal information. This regulatory action reflects growing concern about browser-based threats to data security.
As web applications replace traditional desktop software, browsers become increasingly central to both personal and professional computing. This shift expands the attack surface represented by browser extensions, making them more attractive targets for cybercriminals seeking access to sensitive data and financial systems.
Security experts warn that AI-focused extensions present particular risks due to their popularity and the sensitive nature of AI conversations. LayerX Security consultant Natalie Zargarov noted that
"GPT optimizers will soon become as popular as (not more than) VPN extensions,"
creating opportunities for malicious actors to exploit user trust in AI tools.
The ongoing challenge involves balancing a thriving extension ecosystem with user protection. This requires continued evolution of review processes, improved detection capabilities, and user education about extension risks.
Security researchers emphasize that browser extensions represent a "materially expanded browser attack surface" that demands increased attention from both developers and users.
