Security researcher Orange Tsai has revealed an exploit chain for Microsoft Edge that combines five bugs and two Windows features to run code outside the browser sandbox.

Published on October 28, 2026, the research shows how flaws in browser logic can turn a malicious webpage into code execution on Windows without memory corruption.

Tsai, a member of DEVCORE, built the chain for Pwn2Own Berlin 2026. His technical write-up describes two months of research completed without AI tools. The finished exploit used fewer than 100 lines of code.

The chain began in Edge’s Conditional Access navigation handler, which helps users switch to the right browser profile when accessing Microsoft services. When the supplied email matched the current profile, the handler started a new navigation using a supplied destination.

The crucial mistake was failing to bind that navigation to its original tab. Instead, Chromium used the active tab, letting JavaScript intended for one context run on another website. This created universal cross-site scripting, or UXSS, which breaks the boundary that normally keeps websites apart.

Microsoft Edge Zero-Click Exploit

Because the navigation came from the browser process, Tsai reported that it could also bypass Content Security Policy protections. However, several checks still stood between this finding and an automatic attack.

First, Edge checked whether navigation came from a trusted Microsoft site, but failed to account for another window controlling that navigation. A cross-window flow bypassed this check. Separately, a hardcoded popup exception allowed the researcher to open a window without the usual user click.

The chain also needed a signed-in Edge profile and its email address. In the tested setup, Microsoft’s OneAuth feature could automatically create and sign in a profile using an existing Microsoft account when visiting a Microsoft website.

A cross-origin resource sharing misconfiguration on assets.msn.com then exposed the signed-in email to another website. Together, these steps removed the need for further clicks after attacker-controlled content loaded. The zero-click label therefore describes the automated chain, not an attack requiring no exposure to malicious web content.

Running JavaScript across websites was not enough to execute Windows code. Tsai next targeted Edge’s Immersive Reader, whose read:// address scheme was missing from the list blocking JavaScript URLs on privileged browser pages.

This exposed a native feedback function that packaged diagnostic logs. Path traversal and null-byte handling let the researcher write files outside the intended temporary folder and remove the enforced JSON extension. Cybersecurity News previously covered the related Edge feedback-log code execution vulnerability.

Tsai then changed protocols.json, an Edge configuration file controlling which websites may launch external protocol handlers. This allowed a webpage to invoke the Windows telnet handler. By placing a small executable in a writable directory Windows searches, he achieved code execution outside Edge’s sandbox.

Unlike the separately reported Edge memory-corruption vulnerability, this chain relied on logic errors and trusted features working together.

It shows why browser security reviews must test how navigation, identity, privileged pages, and Windows integrations interact, rather than checking each feature alone. Users should keep Edge updated through Microsoft’s security releases and avoid treating browser isolation as a complete defense.

Give your SOC the alert context to stops incidents quickly. Integrate Threat Intel from 16K SOCs.

The post Microsoft Edge Zero-Click Exploit Chains Five Flaws to Execute Code and Escape Sandbox appeared first on Cyber Security News.