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Known exploited · Synacor

CVE-2018-6882: Synacor Zimbra Collaboration Suite (ZCS) Cross-Site Scripting (XSS) Vulnerability

What it is

Synacor Zimbra Collaboration Suite (ZCS) contains a cross-site scripting vulnerability that might allow remote attackers to inject arbitrary web script or HTML.

Added April 19, 2022Due May 10, 2022CISA KEV catalog 2026.10.01

Vendor
Synacor
Product
Zimbra Collaboration Suite (ZCS)
Added to KEV
April 19, 2022
CISA due date
May 10, 2022
Ransomware use
Known

What CISA requires

Apply updates per vendor instructions.

Forensic triage

No

What to do now

  1. Find every instance of Zimbra Collaboration Suite (ZCS) you run, including the forgotten ones, and check its version against the vendor advisory.
  2. Apply the vendor's fix or mitigation, before May 10, 2022 if you are bound by CISA's deadline, sooner if it faces the internet.
  3. Assume it was tried against you already: look for signs of exploitation from the date it was added, not from the day you patched.
  4. Until every instance is patched, block the attack at the edge: a WAF in blocking mode stops cross-site scripting payloads.

References

CVE-2018-6882 in the National Vulnerability Database

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Block it at the edge while you patch

The Dome's WAF runs the OWASP Core Rule Set in blocking mode and stops cross-site scripting payloads before they reach your application.

See the Dome

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Source: CISA Known Exploited Vulnerabilities Catalog (public domain), catalog version 2026.10.01.