The most interesting thing about the new SearchLeak attack on Microsoft 365 Copilot isn't any single bug. It's that none of the three pieces was dangerous on its own. Varonis combined a prompt injection via a URL parameter, an HTML rendering race condition, and a server-side request forgery in Bing's image search. Each of these is a common bug that security teams usually consider minor. But when you put them together with a Copilot that can access your mailbox, OneDrive, and SharePoint, they create a critical flaw. Microsoft has since patched this issue (CVE-2026-42824).
This is how the attack worked:
* The victim clicks a link. That's the whole interaction. They type nothing.
* The link instructs Copilot to search the mailbox, find sensitive information such as access codes, and place it into an image URL.
* Bing retrieves that image, which sends the stolen data to the attacker's server. Bing serves as the delivery service, allowing the attack to bypass the content security policy intended to stop it.
From the user's perspective, Copilot just pauses for a moment. There is no visible sign that any data has been taken.
In the past, we've spent years rating bugs by their severity on their own. An SSRF here, an HTML injection there—each seemed minor. But when an AI assistant can follow instructions from untrusted input and access your real data, those minor bugs become much more serious. Old types of vulnerabilities become important again in this new context.
If your company uses Copilot or any AI assistant that can access company data, it is important to ask your team how they are rating bugs that affect it. The way we judge what is low risk has changed.
#AI #Cybersecurity #InfoSec #security #privacy #cloud #AttackChain









