bleeping-computer Jul 10, 2026 · Crawled Jul 10, 2026

Zimbra urges customers to patch critical web client XSS flaw

4 Actors 2 CVEs

AI Summary

Zimbra has urged customers to patch a critical stored cross-site scripting (XSS) vulnerability in its Classic Web Client, which could allow attackers to execute malicious code via specially crafted emails. The flaw affects Zimbra Collaboration Suite users and could lead to theft of session data, account settings, or mailbox contents. Although no CVE has been assigned yet, the vulnerability was reported by Google's Threat Analysis Group and is suspected to be exploited by state-backed actors, particularly Russian-linked groups.

AI-extracted · verify before operational use

Extracted Entities 6 found

Threat Actor Winter Vivern → Threat Actor APT29 → Threat Actor UNC2452 → Threat Actor APT28 → CVE CVE-2025-66376 → CVE CVE-2025-48700 →

MITRE ATT&CK TTPs 25 techniques

T1059.001 PowerShell · Execution T1027 Obfuscated Files or Information · Defense Evasion T1055 Process Injection · Defense Evasion T1071.004 DNS · Command And Control T1078.004 Cloud Accounts · Defense Evasion T1090 Proxy · Command And Control T1114 Email Collection · Collection T1204.002 Malicious File · Execution T1556.005 Reversible Encryption · Credential Access T1558.003 Kerberoasting · Credential Access T1566 Phishing · Initial Access T1003.001 LSASS Memory · Credential Access T1059.003 Windows Command Shell · Execution T1070.004 File Deletion · Defense Evasion T1071 Application Layer Protocol · Command And Control T1071.001 Web Protocols · Command And Control T1071.003 Mail Protocols · Command And Control T1082 System Information Discovery · Discovery T1110 Brute Force · Credential Access T1190 Exploit Public-Facing Application · Initial Access T1203 Exploitation for Client Execution · Execution T1485 Data Destruction · Impact T1496 Resource Hijacking · Impact T1539 Steal Web Session Cookie · Credential Access T1557 Adversary-in-the-Middle · Credential Access