A security feature bypass vulnerability exists when Microsoft Edge improperly handles extension requests and fails to request host permission for all_urls. An attacker who successfully exploited this vulnerability could trick a browser into installing an extension without the user's consent.
To exploit the vulnerability, the user must either browse to a malicious website or be redirected to it. In an email attack scenario, an attacker could send an email message in an attempt to convince the user to click a link to a malicious site, which then can download an extension for all_urls without the user's knowledge.
In a web-based attack scenario, an attacker could host a specially crafted website designed to appear as a legitimate website to the user. However, the attacker would have no way to force the user to visit the specially crafted website. The attacker would have to convince the user to visit the specially crafted website, typically by way of an enticement in an email or instant message.
The security update addresses the vulnerability by correcting how Microsoft Edge handles host permissions for adding extensions.