CalPhishing Campaigns Use Outlook Calendar Invites to Deliver Persistent Phishing Lures

Gbhackers •Mayura Kathir • June 23, 2026

A growing trend in which attackers weaponize Microsoft 365 collaboration features to deliver persistent phishing lures via Outlook calendar invites. By abusing Microsoft 365 Groups and Outlook calendar functionality, threat actors move malicious intent out of a single suspicious message and into routine productivity workflows, increasing the chance that targets will treat the interaction as […]

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Phishing Campaigns Exploit Microsoft 365 Collaboration Features Cyber attackers are increasingly leveraging Microsoft 365 collaboration tools, specifically Outlook Groups and calendar invites, to execute phishing campaigns. This method disguises malicious activities within routine workflows, making it difficult for users to identify threats. The technique involves sending what appears to be legitimate group additions or calendar updates, which can lead users to take harmful actions. Fortra's Security Engineer, Daud Jawad, highlighted that this approach shifts the focus from a single suspicious email to a more trusted environment, increasing the likelihood of user engagement. As a result, organizations using Microsoft 365 may face heightened risks of falling victim to these sophisticated phishing attempts. The current status indicates a growing trend in such attacks, necessitating increased vigilance among users and IT departments. 3 sources 52

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CalPhishing Campaigns Use Outlook Calendar Invites to Deliver Persistent Phishing Lures

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