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Unlock with Pro - from £29/user/moDetect Pheditor Hardcoded Default Administrator Credential Exploitation (CVE-2026-55579) in Microsoft Sentinel
Detects authentication and post-authentication activity consistent with exploitation of CVE-2026-55579, a hardcoded default password ('admin') in Pheditor (composer package pheditor/pheditor) versions >= 2.0.1 and < 2.0.6. The vulnerability (CWE-798) allows any unauthenticated attacker with network access to the application to log in using the well-known default credential and achieve full application compromise, since the application does not force a password change on first login. Detection logic focuses on successful logins using the literal 'admin' credential pair, rapid login attempts against the default account, and suspicious follow-on activity (admin panel access, plugin/file upload, config changes) shortly after such a login.
MITRE ATT&CK
KQL Detection Query
let DefaultCred = "admin";
let Window = 30m;
let AdminLogins = (union isfuzzy=true
(W3CIISLog | where cs_username =~ DefaultCred and sc_status in (200,302) | project TimeGenerated, SourceIP=c_ip, User=cs_username, Method=cs_method, Uri=cs_uri_stem)
,(AppServiceHTTPLogs | where CsUsername =~ DefaultCred | project TimeGenerated, SourceIP=CIp, User=CsUsername, Method=CsMethod, Uri=CsUriStem)
);
AdminLogins
| summarize LoginCount=count(), FirstSeen=min(TimeGenerated), LastSeen=max(TimeGenerated), Uris=make_set(Uri) by SourceIP, User
| where LoginCount >= 1
| extend Duration = LastSeen - FirstSeen
| project FirstSeen, LastSeen, SourceIP, User, LoginCount, UrisIdentifies successful or attempted authentications to the Pheditor application using the hardcoded default 'admin' credential, correlating IIS/App Service HTTP logs for login endpoints and admin panel access.
Data Sources
Required Tables
False Positives & Tuning
- Legitimate administrator who has not yet rotated the default password post-patch
- Internal QA/staging environments intentionally using default credentials
- Automated vulnerability scanners authorized to test with default creds
Other platforms for CVE-2026-55579
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 1Simulate Default Credential Login Attempt
Expected signal: HTTP POST request to /login containing username=admin in the request body, followed by a 200/302 response and session cookie issuance.
- Test 2Simulate Post-Login Admin Panel Access
Expected signal: Authenticated HTTP GET request to /admin/dashboard using the session cookie obtained from the default-credential login.
- Test 3Simulate Malicious Plugin Upload via Compromised Admin Session
Expected signal: HTTP POST multipart file upload request to the plugin upload endpoint from an authenticated 'admin' session, followed by creation of a new file in the Pheditor plugins directory.
- Test 4Windows-Based Simulated Login Attempt via PowerShell
Expected signal: Outbound HTTP POST request from the test host to the Pheditor login endpoint containing the default credential pair, logged in network/proxy telemetry.
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