Zero-click XSS in Zimbra Collaboration Classic UI
CVE-2025-48700 is a cross-site scripting vulnerability in Synacor Zimbra Collaboration Suite (ZCS) Classic UI affecting 8.8.15, 9.0, 10.0, and 10.1. The flaw is caused by insufficient sanitization of attacker-controlled HTML content in email messages, including crafted tag structures and attribute values using @import and related script-injection vectors. When a victim views a malicious email in the Zimbra Classic UI, arbitrary JavaScript can execute in the context of that user’s authenticated webmail session. The issue has been described as zero-click in the sense that no additional interaction beyond opening/viewing the message in Classic UI is required. Supporting content also indicates active exploitation in the wild and inclusion in CISA’s KEV catalog.
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Impact, mitigation & remediation
What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.
Impact
What an attacker gets, and what they’ve been doing with it.
Mitigation
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Remediation
Patch, then assume compromise.
Exploits
No public exploits tracked yet. Mallory keeps watching.
No public exploit code observed for this vulnerability.
Affected products & vendors
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
Recent activity
23 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
Roundcube webmail vulnerability exploited in 2025 campaigns.
An unauthenticated cross-site scripting vulnerability in Zimbra Collaboration Suite that can expose sensitive information by executing arbitrary JavaScript in a user's session when a malicious email is viewed in the Classic UI.
A Zimbra Collaboration Suite cross-site scripting vulnerability that allows unauthenticated attackers to execute arbitrary JavaScript in a victim's session and access sensitive information, including via malicious email viewed in the Zimbra Classic UI.
A cross-site scripting vulnerability in Synacor Zimbra Collaboration Suite linked to exploitation campaigns delivering malicious scripts for session hijacking or credential theft.
The version that knows your environment.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.