Security researcher Orange Tsai of DEVCORE has published details of an exploit chain that can turn a malicious webpage into code running outside Microsoft Edge’s security sandbox on Windows.
The technique relies entirely on logic flaws rather than memory corruption, demonstrating how weaknesses in ordinary browser features can be combined to achieve a much more serious security impact.
The exploit chain won $175,000 at the Pwn2Own Berlin 2026 hacking competition in May. Microsoft patched the affected Edge vulnerabilities shortly after the contest, and Tsai published his full technical analysis on October 28. There is currently no evidence that the exploit has been used against real-world targets.
Browser sandboxes are designed to isolate websites from the underlying operating system, preventing malicious pages from directly accessing sensitive resources or executing programs on a victim’s computer. Tsai’s research demonstrates how several seemingly unrelated weaknesses can undermine those protections when chained together. The complete exploit reportedly contains fewer than 100 lines of code.
The first stage creates a universal cross-site scripting (UXSS) capability, allowing JavaScript to execute in the context of websites beyond the one that originally loaded the malicious content. This can bypass protections normally enforced by the browser, including content security policies. The researcher achieved this by exploiting a flaw in Edge’s conditional access navigation throttling feature, which is designed to support business sign-in workflows.
The chain combines additional weaknesses in Edge’s navigation handling, popup restrictions, automatic sign-in behavior and cross-origin protections. Together, these issues allow the attack to progress without requiring the victim to click through a series of prompts. Some of the steps depend on the victim already being signed in to Microsoft services, while a separate cross-origin configuration issue exposes information that helps the attack proceed.
However, executing JavaScript across websites does not automatically provide control over the operating system. To escape the browser sandbox, Tsai found a way to abuse Edge’s Immersive Reader feature, which operates under a special internal URL scheme. A missing restriction allowed the chain to reach functionality that was intended for internal browser operations rather than untrusted web content.
The researcher then demonstrated how this access could be combined with a file-writing weakness in an internal diagnostic utility to reach operating-system-level code execution. The final stage abuses Windows protocol-handler behavior to launch an attacker-controlled program, completing the escape from the browser’s sandbox.
Microsoft addressed the relevant Edge vulnerabilities in Stable version 148.0.3967.70, released on May 15, 2026. The fixes include CVE-2026-45492, CVE-2026-45494 and CVE-2026-45495. Microsoft’s records describe individual issues involving security feature bypass and spoofing, with reported CVSS scores of 5.4 for the first two vulnerabilities. Those individual ratings do not necessarily reflect the potential impact of combining several flaws into a complete exploit chain.
The demonstration was conducted as part of a security competition, rather than an observed attack against ordinary users. Tsai also noted that one step used in the demonstration was convenient for the competition but was not essential to a practical attack. The research later received a 2026 Pwnie Award for Epic Achievement.
For users, the main takeaway is to ensure Microsoft Edge is running a current, supported version with security updates installed. The specific vulnerabilities described in the research have already been patched, so systems running the fixed browser version are not affected by this particular exploit chain. Organizations should also maintain their normal browser update policies and monitor security advisories for newly discovered vulnerabilities.
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