A remote code execution vulnerability exists when the Windows Text Service Module improperly handles memory. An attacker who successfully exploited the vulnerability could gain execution on a victim system. An attacker could host a specially crafted website that is designed to exploit the vulnerability through Microsoft Edge (Chromium-based), and then convince a user to view the website. The attacker could also take advantage of compromised websites and websites that accept or host user-provided content or advertisements by adding specially crafted content that could exploit the vulnerability. In all cases, however, an attacker would have no way to force users to view the attacker-controlled content. Instead, an attacker would have to convince users to take action, typically by way of enticement in an email or Instant Messenger message, or by getting them to open an attachment sent through email. The security update addresses the vulnerability by correcting how the Windows Text Service Module handles memory.
Liu Long of Ant Group Light-Year Security Lab, cc working with <a href="https://www.zerodayinitiative.com/">Trend Micro's Zero Day Initiative</a>