The cybersecurity landscape witnessed a concerning development as threat actors discovered a novel attack vector targeting Microsoft Edge’s Internet Explorer mode functionality.
This sophisticated campaign emerged in August 2025, exploiting the inherent security weaknesses of legacy browser technology to compromise unsuspecting users’ devices.
The attack represents a significant evolution in threat actor tactics, demonstrating their ability to weaponize seemingly benign compatibility features.
The attack methodology combines social engineering with zero-day exploits targeting Internet Explorer’s Chakra JavaScript engine. Cybercriminals initially direct victims to carefully crafted spoofed websites that appear legitimate, creating a false sense of security.
Once victims arrive at these malicious sites, attackers deploy a strategic flyout notification requesting users to reload the page in Internet Explorer mode, effectively transitioning them from Edge’s secure Chromium-based environment to IE’s vulnerable legacy framework.
This transition proves critical as Internet Explorer lacks the robust security architecture and defense-in-depth mitigations present in modern browsers.
The legacy environment exposes users to risks that contemporary Chromium-based browsers are specifically engineered to prevent, creating an ideal exploitation opportunity for malicious actors.
Microsoft Edge security analysts identified the threat after receiving credible intelligence about active exploitation campaigns.
The research team discovered that attackers were systematically targeting the compatibility feature designed to support legacy business applications, older security camera interfaces, and government portals that still rely on outdated technologies like ActiveX and Flash.
Chakra Engine Exploitation and Privilege Escalation
The attack’s technical sophistication lies in its multi-stage exploitation process targeting the Chakra JavaScript engine.
After successfully convincing victims to switch to Internet Explorer mode, attackers deploy unpatched zero-day exploits specifically crafted for IE’s JavaScript execution environment.
The Chakra engine, despite Microsoft’s previous hardening efforts, remains vulnerable to memory corruption attacks that enable remote code execution.
Following successful code execution within the browser context, threat actors implement a second exploit designed for privilege escalation.
This secondary payload allows attackers to break out of the browser’s sandboxed environment, gaining elevated system privileges and full device control.
The dual-exploit approach ensures comprehensive system compromise, enabling malware installation, lateral movement within corporate networks, and sensitive data exfiltration.
Microsoft responded by restricting IE mode access, removing high-risk entry points including toolbar buttons and context menus while maintaining enterprise policy support for legitimate business needs.
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