By Microsoft Defender Security Research Team
Publication Date: 2026-03-05 16:02:00
Microsoft Defender has been investigating reports of malicious Chromium‑based browser extensions that impersonate legitimate AI assistant tools to harvest LLM chat histories and browsing data. Reporting indicates these extensions have reached approximately 900,000 installs. Microsoft Defender telemetry also confirms activity across more than 20,000 enterprise tenants, where users frequently interact with AI tools using sensitive inputs.
The extensions collected full URLs and AI chat content from platforms such as ChatGPT and DeepSeek, exposing organizations to potential leakage of proprietary code, internal workflows, strategic discussions, and other confidential data.
At scale, this activity turns a seemingly trusted productivity extension into a persistent data collection mechanism embedded in everyday enterprise browser usage, highlighting the growing risk browser extensions pose in corporate environments.
