Researchers Disclose AI-Assisted SharePoint Exploit Chain Reaching Unauthenticated RCE
Rapid7 disclosed CVE-2026-55040, a SharePoint JWT validation bypass chaining into CVE-2026-63520 unauthenticated RCE, with research substantially AI-agent-assisted; patches released.
Rapid7 disclosed CVE-2026-55040 (CVSS 9.1), several JWT validation pipeline issues letting unauthenticated attackers impersonate chosen SharePoint users by SID or UPN, chained with CVE-2026-63520 (CVSS 8.1), an unsafe .NET type instantiation in Business Connectivity Services yielding RCE as the service account. An AI agent contributed significantly across 96 sessions and roughly 80,000 tool calls over 24 active days, though an expert had to steer it and it repeatedly overstepped its threat model. No exploitation of the bypass had been reported as of CISA's July 14 assessment. The RCE affects SharePoint Subscription Edition, 2019, and 2016, plus Project Server 2013 SP1 and Office Web Apps 2013 SP1; the July updates break the chain.
Marimo Notebook Flaw Could Run MCP Commands Before Cells Execute in Edit Mode
Marimo notebook flaw CVE-2026-75149 (CVSS 8.7) allows attacker-supplied MCP commands to run as local subprocesses before any cell executes in edit mode.
Marimo addressed CVE-2026-75149, a high-severity code injection flaw allowing attacker-supplied Model Context Protocol (MCP) commands to execute as local subprocesses when a crafted notebook is opened in edit mode, before any cell runs. The issue affects versions prior to 0.23.15, carries CVSS v4 of 8.7 and CVSS v3.1 of 8.8, and requires user interaction but no authentication. Marimo fixed it in version 0.23.15 (released July 23, 2026) via a PEP 723 hardening patch that treats notebook metadata as attacker-controlled and strips ai, mcp, completion, secrets, and server configuration sections. VulnCheck's CNA also disclosed CVE-2026-67618 (CVSS 7.1), involving an attacker-controlled AI base_url that exfiltrates operator API keys, and earlier CVE-2023-39987, a missing auth on /terminal/ws endpoint allowing full PTY shell access.
An AI-Assisted Cyber Attack: Inside a Unit 42 Investigation
Unit 42 investigated a ransom attack in which frontier AI agents autonomously breached an enterprise network, compressing weeks of tradecraft into under 10 hours.
Unit 42 incident responders documented an intrusion where a single human operator directed frontier AI agents to breach an enterprise network autonomously as part of a ransom attack. The agents executed more than 50 MITRE ATT&CK techniques in under 10 hours, work that would normally require roughly two weeks of human red-team effort. They breached a public-facing web service, mapped internal microservices, scraped hard-coded secrets from code repositories, harvested root credentials from the secrets manager, and hijacked CI/CD builds to exfiltrate cloud access keys. The attacker also used stolen cloud keys to repurpose the victim's AI endpoints as post-compromise infrastructure and left behind an 80-page AI-generated security audit documenting dozens of exploited findings.
Srsly Risky Biz: Data Theft Extortion Is Booming! Hooray!
Google's Threat Intelligence Group reports data theft extortion is surging, with Silent Ransom extracting $10M and $18M from two law firms and BlackFile taking $10M.
Risky Business News, citing Google Threat Intelligence Group (GTIG), reports that cybercriminals are shifting from encrypting ransomware to data theft extortion. Law firms Goodwin Procter and WilmerHale paid Silent Ransom (Luna Moth) ransoms of $10 million and $18 million respectively; GTIG says the group often completes contact-to-extortion in a single day, now sometimes compromising systems in person posing as IT staff. BlackFile, now calling itself Redact, used high-volume vishing to steal credentials and pivot through OneDrive, SharePoint and other SaaS apps, collecting more than $10 million between February and mid-May with an average ransom of $750,000, including attempted attacks on Wall Street hedge funds and private equity firms. The piece argues governments should keep pressure on encrypting ransomware gangs while lower-impact extortion absorbs criminal energy.