Cisco Talos IR Q2 2026: Observed Attack Chains of M365 Token Compromise and RMM-Disguised Ransomware

Cisco Talos IR Q2 2026: Observed Attack Chains of M365 Token Compromise and RMM-Disguised Ransomware 1. Basic Information Article Title : IR Trends Q2 2026: Phishing and weaponized remote management tools drive attack chains Publisher : Cisco Talos Blog Publication Date : July 28, 2026 Original Article : https://blog.talosintelligence.com/ir-trends-q2-2026/ Related Sources : ARToken technical analysis and Talos IR observations within the article Related Entities : UAT-11764, ARToken, EvilTokens, Sinobi, Warlock/Storm-2603, MeshAgent/MeshCentral, Zoho Assist, Microsoft 365, SharePoint, OneDrive, RDP, WinRM, rclone Severity : High 2. Executive Summary Talos IR identified real-world attack chains from recent incidents. The first chain steals M365 tokens using QR code PDFs and OAuth device-code phishing, then self-propagates through inbox rules, SharePoint, and mass internal emails. The second chain uses modified and abused legitimate RMM tools to achieve SYSTEM persistence, lateral movement, and domain-wide ransomware deployment via GPO. 3. Attack Flows Chain A: UAT-11764 QR Phishing The attacker sends targeted PDFs from a compromised M365 account. The victim scans the PDF's QR code using a mobile device. Credentials are stolen on a fake M365 login page. The attacker signs in to the Microsoft account. Inbox rules are created to hide warnings and replies. Malicious documents are placed in SharePoint. The attacker uses contacts to resend phishing emails internally and externally. Chain B: M365 Token Compromise via ARToken Lures pretending to be trusted vendors are presented. The user is redirected to the Microsoft OAuth device authorization flow. The user approves the attacker's device code on a legitimate Microsoft screen. Access tokens are obtained without stealing passwords, bypassing MFA. ARToken manages tokens using over 80 APIs. Persistence is achieved via PRT, followed by email/BEC, inbox rule manipulation, and OneDrive/SharePoint management and exfiltration. Toke