New BitB Phishing Attack Targets Microsoft 365 Logins

Gbhackers •Mayura Kathir • June 9, 2026

A new Browser-in-the-Browser (BitB) phishing campaign is abusing fake OAuth login windows to steal Microsoft 365 credentials, and its design is polished enough to bypass casual visual checks. The attack uses a draggable popup that mimics a real browser dialog. However, it is embedded in the page itself and paired with a spoofed Microsoft OAuth […]

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This article is one source in a clustered incident — the cluster page carries the summary, timeline and every other outlet covering it.

New Browser-in-the-Browser Phishing Attack Targets Microsoft 365 Users A sophisticated Browser-in-the-Browser (BitB) phishing campaign has emerged, specifically targeting Microsoft 365 users. The attack employs a highly convincing fake OAuth login window that is difficult to distinguish from legitimate prompts, making it easy for even experienced users to be deceived. This attack vector is embedded within the web page, allowing the fake login to appear as part of the browser interface. As a result, users may unknowingly submit their credentials, leading to potential account compromise. The campaign's design is polished enough to bypass casual visual checks, raising concerns about its effectiveness. Currently, there are no specific numbers on the scale of the attack or confirmed incidents reported. Security experts are urging users to remain vigilant and verify login prompts carefully. The situation is ongoing, with no known mitigation strategies disclosed yet. 3 sources 63

Extracted Entities

New BitB Phishing Attack Targets Microsoft 365 Logins

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Extracted Entities

Attack Types (1)

MITRE ATT&CK (1)

Platforms (1)

Tools (1)