Pen Test Partners, a renowned cybersecurity and penetration testing firm, recently exposed a critical vulnerability in Microsoft’s Copilot AI for SharePoint. Known for simulating real-world hacking scenarios, the company’s redteam specialists investigate how systems can be breached just like skilled threatactors would attempt in real-time. With attackers increasingly leveraging AI, ethical hackers are now adopting similar methods—and the outcomes are raising eyebrows.

In a recent test, the Pen Test Partners team explored how Microsoft Copilot AI integrated into SharePoint could be manipulated. They encountered a significant issue when a seemingly secure encrypted spreadsheet was exposed—simply by instructing Copilot to retrieve it. Despite SharePoint’s robust access controls preventing file access through conventional means, the AI assistant was able to bypass those protections.

“The agent then successfully printed the contents,” said Jack Barradell-Johns, a red team security consultant at Pen Test Partners, “including the passwords allowing us to access the encrypted spreadsheet.”

This alarming outcome underlines the dual-nature of AI in informationsecurity—it can enhance defenses, but also inadvertently open doors to attackers if not properly governed.

Barradell-Johns further detailed the engagement, explaining how the red team encountered a file labeled passwords.txt, placed near the encrypted spreadsheet. When traditional methods failed due to browser-based restrictions, the hackers used their red team expertise and simply asked the Copilot AI agent to fetch it.

“Notably,” Barradell-Johns added, “in this case, all methods of opening the file in the browser had been restricted.”

Still, those download limitations were sidestepped. The AI agent output the full contents, including sensitive credentials, and allowed the team to easily copy the chat thread, revealing a potential weak point in AI-assisted collaborationtools.

This case serves as a powerful reminder: as AItools become more embedded in enterprise workflows, their securitytesting must evolve in step. It's not just about protecting the front door—it’s about teaching your digital assistant not to hold it open for strangers.

For those interested in the full technical breakdown, the complete Pen Test Partners report dives into the step-by-step methods used and broader securityimplications of Copilot’s current design.

Davey Winder reached out to Microsoft, and a spokesperson said:

“SharePoint information protection principles ensure that content is secured at the storage level through user-specific permissions and that access is audited. This means that if a user does not have permission to access specific content, they will not be able to view it through Copilot or any other agent. Additionally, any access to content through Copilot or an agent is logged and monitored for compliance and security.”

Further, Davey Winder then contacted Ken Munro, founder of Pen Test Partners, who issued the following statement addressing the points made in the one provided by Microsoft.

“Microsoft are technically correct about user permissions, but that’s not what we are exploiting here. They are also correct about logging, but again it comes down to configuration. In many cases, organisations aren’t typically logging the activities that we’re taking advantage of here. Having more granular user permissions would mitigate this, but in many organisations data on SharePoint isn’t as well managed as it could be. That’s exactly what we’re exploiting. These agents are enabled per user, based on licenses, and organisations we have spoken to do not always understand the implications of adding those licenses to their users.”