Loading story…
Attackers with access to a Microsoft 365 identity or app context can accelerate post-compromise reconnaissance and data discovery by using built-in AI assistants and Microsoft Graph at scale. Varonis warns that Microsoft 365 Copilot inherits the logged-in user’s permissions, turning a compromised account (e.g., via phishing kits) into a natural-language interface for quickly locating sensitive content across SharePoint, OneDrive, and Exchange; this can reduce the volume and distribution of traditional “click-by-click” access events and shift activity into Copilot query patterns, changing the forensic footprint defenders typically rely on.
Separately, a red-team toolkit called M365Pwned was released as two PowerShell 5.1 WinForms GUI tools—MailPwned-GUI.ps1 (Exchange Online/Outlook) and SharePwned-GUI.ps1 (SharePoint/OneDrive)—that enumerate, search, and exfiltrate tenant data using the Microsoft Graph API with application-level OAuth (admin-consented) permissions and authentication via client secret, certificate thumbprint, or raw access token (“pass-the-token”). The tooling highlights how application permissions can enable broad tenant-wide mailbox and file access (e.g., global keyword searches, bulk attachment downloads, document preview/download, and impersonation email composition), reinforcing the risk that over-permissioned identities/apps and weak governance in M365 can turn post-compromise recon into fast, high-impact data access.
Get the actors, campaigns, and ATT&CK mapping behind it.
3 events from the most recent confirmed update back to the earliest known activity.
Varonis Threat Labs disclosed a demonstration called 'Reprompt,' described as a single-click Copilot attack that exfiltrates personal data by hijacking an authenticated session and relaying requests through an attacker-controlled server. The disclosure highlighted how AI assistants can be abused after account compromise to speed discovery and data theft.
Varonis published analysis arguing that Microsoft 365 Copilot can materially change post-compromise reconnaissance by allowing attackers with stolen credentials or session tokens to query and summarize data the compromised user can access across SharePoint, OneDrive, Exchange, and Teams. The report framed oversharing and excessive permissions in Microsoft 365 as the core risk and recommended least-privilege enforcement and tighter data access controls.
A red teamer using the handle OtterHacker publicly released M365Pwned, a pair of PowerShell WinForms GUI tools for enumerating, searching, and exfiltrating Microsoft 365 data through the Microsoft Graph API using application-level OAuth tokens. The release included MailPwned for Exchange Online/Outlook and SharePwned for SharePoint/OneDrive, with support for multiple authentication methods and sovereign/GCC cloud routing.
Vulnerabilities, threat actors, malware, products, organizations, and breaches Mallory has linked to this story.
Get the adversaries, campaigns, and ATT&CK mapping behind this technique, with detections ready to deploy.
2 references tracked. Mallory keeps watching after this page renders.
Map indicators from this story to your assets and identify affected systems in minutes.
Every observed campaign, victim, and pivot linked to actors named in this story.
Malware, exploits, and IOCs connected to the activity described here.
YARA, Sigma, and Snort rules deployed to your SIEM as soon as they’re published.
Get matching new stories delivered to your team as they break — not the next morning.
Ask questions about this story and take action on the answers.
Other stories Mallory is tracking that overlap on entities, sources, or topic labels.
Security researchers have identified two distinct attack techniques targeting Microsoft's AI-powered platforms. The first, dubbed **CoPhish**, leverages Microsoft Copilot Studio agents to deliver fraudulent OAuth consent requests through legitimate Microsoft domains, enabling attackers to steal OAuth tokens. By customizing Copilot Studio chatbots and exploiting the platform's "demo website" feature, attackers can trick users into authenticating with malicious applications, potentially granting unauthorized access to sensitive resources. Microsoft has acknowledged the issue and is working on product updates to mitigate the risk, emphasizing the need for organizations to strengthen governance and consent processes. Separately, a vulnerability in Microsoft 365 Copilot was discovered that allowed attackers to use indirect prompt injection via Mermaid diagrams to exfiltrate sensitive tenant data, such as emails. By embedding malicious instructions in seemingly benign prompts, attackers could manipulate Copilot to retrieve and encode confidential information. Although Microsoft has since patched this flaw, the incident highlights the emerging risks associated with integrating AI assistants and third-party tools, as well as the challenges in securing complex, automated workflows within enterprise environments.
Jul 12, 2026
Attackers are increasingly leveraging Microsoft Copilot Studio to facilitate OAuth phishing attacks by exploiting its ability to host customizable agents and redirect users to arbitrary URLs. Security researchers have demonstrated that Copilot Studio agents, which appear as legitimate Microsoft services, can be configured with a 'Login' button that redirects unsuspecting users to malicious OAuth consent pages. This technique increases the credibility of phishing attempts, as the initial interaction occurs on a trusted Microsoft domain, making it more likely for users to grant permissions to malicious applications. Once a user consents, attackers can exfiltrate OAuth tokens, granting them persistent access to sensitive data and services within the victim's Microsoft 365 environment. The flexibility of Copilot Studio, while beneficial for legitimate automation, also provides attackers with a powerful tool to craft convincing phishing lures and automate token exfiltration. Security experts emphasize the importance of reviewing and tightening Entra ID application consent policies, especially in light of recent and upcoming policy updates from Microsoft. Despite improvements in consent policy enforcement, risks remain, particularly when users with elevated privileges, such as Application Administrators, are able to grant broad permissions. In parallel, security researchers have highlighted the prevalence of hidden malicious OAuth applications within Microsoft 365 tenants. Open-source tools like Cazadora have been developed to help administrators audit their environments for suspicious applications, such as those with anomalous names or reply URLs. Common indicators of malicious OAuth apps include names mimicking user accounts, generic test names, or non-alphanumeric strings, as well as reply URLs pointing to local loopback addresses. The discovery of even a single suspicious app often signals a broader compromise, underscoring the need for comprehensive audits. Security teams are urged to regularly inspect both Enterprise Applications and Application Registrations for signs of abuse. The combination of sophisticated phishing techniques using Copilot Studio and the widespread presence of malicious OAuth apps represents a significant threat to Microsoft 365 environments. Proactive monitoring, user education, and strict consent policies are critical to mitigating these risks. Organizations should remain vigilant for new attack vectors that exploit trusted cloud services. The evolving landscape of OAuth-based attacks requires continuous adaptation of security controls and incident response strategies. Collaboration between security researchers and cloud service providers is essential to stay ahead of emerging threats. The integration of automation and AI-driven services like Copilot Studio into enterprise environments necessitates a reevaluation of traditional security assumptions. As attackers continue to innovate, defenders must leverage both technical controls and threat intelligence to protect their organizations.
Jun 29, 2026
Attackers abused Microsoft’s legitimate authentication and Microsoft 365 infrastructure to run phishing and business email compromise campaigns without relying on fake login pages. Check Point observed more than 200 phishing emails sent to about 120 organizations across industries and countries, using Microsoft Planner-style notifications about HR, payroll, and benefits updates as lures. Victims were directed to a real `login.microsoftonline.com` authorization page and asked to approve a malicious OAuth application, after which Microsoft redirected the browser to an attacker-controlled AWS API Gateway endpoint that captured an authorization token for exchange into Microsoft account access. Researchers said the technique could give attackers broad access to Microsoft 365 data depending on granted permissions, including email, files, Teams chats, SharePoint, OneDrive, and calendar content, creating risks of credential theft, account takeover, data breaches, financial fraud, malware delivery, and BEC. High-value and privileged users, organizations handling sensitive data, tenants using Microsoft ADFS, and general Microsoft 365 users were identified as potential targets. Recommended defenses include enforcing MFA, auditing Microsoft 365 tenant and OAuth application settings, strengthening email and application security controls, applying sign-in risk policies, and training users to scrutinize consent prompts as well as phishing lures.
Aug 11, 2026