Detect Zimbra Collaboration Suite XSS Exploitation (CVE-2025-48700) in Microsoft Sentinel
Detects exploitation of a stored or reflected cross-site scripting (XSS) vulnerability in Synacor Zimbra Collaboration Suite (ZCS). This KEV-listed vulnerability allows attackers to inject malicious scripts into the Zimbra web client, potentially leading to session hijacking, credential theft, or further lateral movement within the organization. XSS in webmail platforms is frequently exploited by threat actors to steal session tokens and pivot to email account compromise.
MITRE ATT&CK
KQL Detection Query
let ZimbraHosts = dynamic(["zimbra", "webmail", "mail"]);
let XSSPatterns = dynamic(["<script", "javascript:", "onerror=", "onload=", "eval(", "document.cookie", "document.location", "window.location", "String.fromCharCode", "atob(", "btoa("]);
let ZimbraXSSPaths = dynamic(["/zimbra/", "/service/soap", "/h/", "/m/", "/B6/"]);
union
(
W3CIISLog
| where csUriStem has_any (ZimbraXSSPaths)
| where csUriQuery has_any (XSSPatterns) or csReferer has_any (XSSPatterns)
| project TimeGenerated, Computer, csUriStem, csUriQuery, csReferer, csUsername, cIP = c_ip, scStatus = sc_status, csUserAgent = cs_User_Agent
),
(
CommonSecurityLog
| where DeviceProduct has_any ("Zimbra", "ZCS")
| where RequestURL has_any (XSSPatterns) or Message has_any (XSSPatterns)
| project TimeGenerated, Computer = DeviceName, csUriStem = RequestURL, csUriQuery = RequestURL, csReferer = "", csUsername = DestinationUserName, cIP = SourceIP, scStatus = tostring(EventOutcome), csUserAgent = RequestClientApplication
)
| where scStatus in ("200", "302", "301") or isempty(scStatus)
| summarize
RequestCount = count(),
UniqueXSSPayloads = dcount(csUriQuery),
SamplePayloads = make_set(csUriQuery, 5),
FirstSeen = min(TimeGenerated),
LastSeen = max(TimeGenerated)
by cIP, csUsername, Computer, bin(TimeGenerated, 5m)
| where RequestCount >= 1
| extend Severity = "High", CVE = "CVE-2025-48700"Detects XSS payload patterns in Zimbra web server access logs and common security log sources. Looks for script injection markers in URI parameters and referrer headers targeting Zimbra-specific URL paths.
Data Sources
Required Tables
False Positives & Tuning
- Security scanner or WAF testing tools that probe for XSS vulnerabilities during authorized penetration tests
- Legitimate email content containing HTML that resembles XSS patterns when logged by the web server
- Automated vulnerability assessment tools running against Zimbra infrastructure
- Browser auto-fill or bookmark data containing special characters that match XSS heuristics
Other platforms for CVE-2025-48700
Testing Methodology
Validate this detection against 4 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1Basic Reflected XSS Probe via Zimbra Search Parameter
Expected signal: Web server access log entry showing GET /zimbra/h/search with q=%3Cscript%3E... URL-encoded payload, HTTP 200 response, source IP of test system
- Test 2Event Handler XSS Payload Delivery via Zimbra URL Parameter
Expected signal: Web server access log showing GET requests to /zimbra/h/compose and /zimbra/h/ with onerror= and onload= patterns in URI query strings, HTTP response codes
- Test 3Simulated Session Cookie Exfiltration via XSS in Zimbra (Post-Exploitation)
Expected signal: Outbound HTTP GET request from Zimbra user's source IP to external attacker-controlled IP containing URL-encoded session token data in the query string; proxy/firewall logs showing unusual outbound connection from Zimbra webmail user IP
- Test 4Stored XSS Payload Submission via Zimbra SOAP API
Expected signal: Zimbra nginx access log showing POST to /service/soap with HTTP 200 response; Zimbra mailbox.log showing CreateContactRequest SOAP operation; POST body (if logged) containing the HTML-encoded XSS payload in the notes field
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