Synacor Zimbra Collaboration Suite (ZCS) Cross-Site Scripting (XSS) Vulnerability
Synacor · Zimbra Collaboration Suite (ZCS)
The flaw is a cross-site scripting (XSS) vulnerability in the Zimbra Classic Web Client, a component of Synacor's Zimbra Collaboration Suite (ZCS) affecting versions 8 before 8.8.15 Patch 41. An attacker can inject script into the web client to run in a victim's browser, which requires network access and no authentication but does require the victim to interact with the crafted content.
Zimbra Collaboration (ZCS) 8 before 8.8.15 Patch 41 allows XSS in the Zimbra Classic Web Client.
- Exploited
- Yes, in CISA KEV
- Reports
- 0
- Tactics
- 1/15
How an attack unfolds
Based on MITRE ATT&CKA public catalogue of the techniques attackers use, maintained by MITRE. Patchfirst uses it to describe what attackers do with a vulnerability. mappings. Select a step to see the evidence.How attackers get in
What they do
Exploitation timelineDated milestones for a CVE: when it was disclosed, when exploit code became public, when exploitation was confirmed, and when threat reports named it.
First seen exploited 32 days before it was disclosed.
- First seen exploitedVulnCheck KEV evidence32 days before
- Added to CISA KEVEU database agrees4 days before
- Disclosedday 0
CISA KEV listing is when exploitation was confirmed, not necessarily the first attack.
MITRE ATT&CKA public catalogue of the techniques attackers use, maintained by MITRE. Patchfirst uses it to describe what attackers do with a vulnerability. techniques
2 TechniqueOne specific attacker behaviour in MITRE ATT&CK, such as T1190 “Exploit Public-Facing Application”. IDs with a dot, like T1059.004, are sub-techniques., grouped by TacticThe attacker’s goal at a stage of an attack in MITRE ATT&CK, such as Initial Access or Persistence. Each technique belongs to one or more tactics. in kill-chain order, 2 cited passages 2ExecutionTA0002
XSS executes attacker JavaScript in browser
allows XSS in the Zimbra Classic Web Client
user clicks malicious link triggering XSS
allows XSS in the Zimbra Classic Web Client
Detection
0 rules for this CVE · 33 general rules for its techniquesRules for this CVE
0Sigma ruleAn open, vendor-neutral detection rule for log data. Security teams convert Sigma rules into searches for their own SIEM. that reference CVE-2023-37580 directly.CVE-specific rules are not available in this build. Search SigmaHQ ↗
General rules for this CVE’s techniques
These detect the technique in general, not this specific vulnerability.
Malicious LinkT1204.0014 general rules
- Symlink Etc Passwdhightest
- Potential ClickFix Execution Pattern - Registryhighexperimental
- Suspicious ClickFix/FileFix Execution Patternhighexperimental
- Suspicious Execution via macOS Script Editormediumtest
JavaScriptT1059.00729 general rules
- Adwind RAT / JRAThightest
- Adwind RAT / JRAT File Artifacthightest
- Csc.EXE Execution Form Potentially Suspicious Parenthightest
- Cscript/Wscript Uncommon Script Extension Executionhightest
- HackTool - CACTUSTORCH Remote Thread Creationhightest
- HackTool - Koadic Executionhightest
- HTML Help HH.EXE Suspicious Child Processhightest
- JXA In-memory Execution Via OSAScripthightest
Sigma rules © SigmaHQ, Detection Rule License 1.1; linked, not reproduced.
What security researchers reported
Not named in any threat report yetAlso mentioned in 50 community threat pulses (AlienVault OTX)
Weaker evidencePulses are indicator collections that anyone can publish. A mention is not confirmation of exploitation.
- Actively_Exploited_Kev | Oct 29, 202628 Oct 2026
- Actively_Exploited_Kev | Oct 28, 202627 Oct 2026
- Actively_Exploited_Kev | Oct 27, 202626 Oct 2026
- Actively_Exploited_Kev | Oct 24, 202623 Oct 2026
- Actively_Exploited_Kev | Oct 23, 202622 Oct 2026
- Actively_Exploited_Kev | Oct 22, 202621 Oct 2026
- 44 more on OTX