CVE-2025-27915 — Synacor Zimbra Collaboration Suite (ZCS) Cross-site Scripting Vulnerability
Severity: Critical · Kind: Vulnerability
What it is
AI offline placeholder summary for: Title: CVE-2025-27915 — Synacor Zimbra Collaboration Suite (ZCS) Cross-site Scri.
Who this affects
AI summarisation is currently disabled — see the source link for the full upstream advisory.
What to do
Re-run summarisation from /admin/threats once ANTHROPIC_API_KEY is configured.
From the source
Synacor Zimbra Collaboration Suite (ZCS). Synacor Zimbra Collaboration Suite (ZCS) contains a cross-site scripting vulnerability that exists in the Classic Web Client due to insufficient sanitization of HTML content in ICS files. When a user views an e-mail message containing a malicious ICS entry, its embedded JavaScript executes via an ontoggle event inside a tag. This allows an attacker to run arbitrary JavaScript within the victim's session, potentially leading to unauthorized actions such as setting e-mail filters to redirect messages to an attacker-controlled address. As a result, an attacker can perform unauthorized actions on the victim's account, including e-mail redirection and data exfiltration. Required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Vulnerability facts
- CVE
- CVE-2025-27915
- On CISA KEV since
- 2025-10-07
- Ransomware use
- Unknown
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Plain-English summaries are AI-generated and reviewed for tone, not technical accuracy. For incident response, always rely on the original source linked above.