## Microsoft Issues Emergency Mitigations for Exchange Zero-Day Under Active Exploitation
Microsoft has confirmed active exploitation of a high-severity vulnerability in Exchange Server that enables threat actors to execute arbitrary code through cross-site scripting attacks targeting Outlook on the web users. The software giant released emergency mitigations as security researchers track the campaign's spread across unpatched deployments.

The flaw allows attackers to leverage crafted XSS payloads within the web-based email interface to bypass security boundaries and run malicious code on affected servers. Microsoft classified the vulnerability as high-severity and urged organizations running Exchange Server to apply available mitigations immediately. The company shared temporary workarounds while a full patch remains in development, indicating the complexity of addressing the underlying code execution pathway.

Security analysts warn that Exchange Server remains a high-value target due to its widespread deployment in corporate email infrastructure and its historical significance as an attack surface for nation-state actors and ransomware groups. The vulnerability's proximity to sensitive communications makes it particularly attractive for espionage-oriented campaigns. Organizations unable to apply mitigations immediately should consider restricting external access to Outlook on the web and monitoring for anomalous email processing activity.
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- **Source**: BleepingComputer Echo RSS
- **Sector**: The Lab
- **Tags**: zero-day, XSS, arbitrary code execution, Microsoft, Exchange Server
- **Credibility**: unverified
- **Published**: 2026-05-15 10:18:31
- **ID**: 83411
- **URL**: https://whisperx.ai/en/intel/83411