Detect Zimbra Collaboration Suite XSS Exploitation (CVE-2025-48700) in CrowdStrike LogScale
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
LogScale Detection Query
#event_simpleName=NetworkConnectIP4 OR #event_simpleName=NetworkReceiveAcceptIP4
| CommandLine = /zimbra|webmail/
| event_platform = "Lin"
| RemoteAddressIP4 != "127.0.0.1"
| RemoteAddressIP4 != "::1"
// Also check for suspicious process execution on Zimbra host following web request
| join (
#event_simpleName IN (ProcessRollup2, SyntheticProcessRollup2)
| ImageFileName IN ("/opt/zimbra/*", "/usr/lib/zimbra/*")
| CommandLine = /<script|javascript:|eval\(|document\.cookie|onerror=|onload=/
BY aid, TargetProcessId
)
BY aid
| groupby([aid, RemoteAddressIP4, UserName, CommandLine, ImageFileName],
function=[
count(as=event_count),
min(timestamp, as=first_seen),
max(timestamp, as=last_seen),
collect(CommandLine, limit=5, as=sample_commands)
]
)
| where event_count >= 1
| eval cve="CVE-2025-48700", severity="high"
| sort(first_seen, order=desc)CrowdStrike Falcon LogScale CQL query to detect XSS-related activity on Zimbra server hosts by correlating network connection events with suspicious process execution containing XSS payload patterns.
Data Sources
Required Tables
False Positives & Tuning
- Automated security scanning tools running on or against Zimbra server infrastructure
- Zimbra administrative scripts that process HTML content containing script-like patterns
- Log analysis tools that parse Zimbra logs containing XSS payload entries from blocked attempts
- Development or staging Zimbra instances used for security testing with XSS payloads
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
Unlock Pro Content
Get the full detection package for CVE-2025-48700 including response playbook, investigation guide, and atomic red team tests.