A recently patched vulnerability in Microsoft Edge could have permitted unauthorized installation of browser extensions, potentially leading to malicious activities on users’ systems. The flaw, identified as CVE-2024-21388, allowed attackers to exploit a private API meant for marketing purposes, bypassing user consent to install extensions. Although addressed in Edge version 121.0.2277.83, disclosed by Guardio Labs researcher Oleg Zaytsev, and credited to Jun Kokatsu, the flaw posed a risk of browser sandbox escape.
Guardio’s findings revealed that the vulnerability enabled attackers to run JavaScript on specific Microsoft-owned websites like bing.com or microsoft.com, facilitating the installation of extensions from the Edge Add-ons store without user interaction. The flaw exploited privileged access to private APIs within the browser, such as edgeMarketingPagePrivate, accessible from whitelisted Microsoft sites. This loophole allowed arbitrary extension installation, evading the need for user consent.
The flaw’s exploitation involved insufficient validation, enabling attackers to stealthily install extensions by providing extension identifiers from the storefront instead of theme identifiers. As the installation occurred without adhering to its original design, no user interaction or consent was required, making the attack vector more dangerous. Although no evidence of real-world exploitation has been found, the vulnerability underscores the potential risks posed by browser customizations and the importance of maintaining a balance between user convenience and security.
