According to the researchers, the attackers did not use a traditional web shell to gain persistent access to the targeted servers. Instead, they used a custom component that demonstrated an in-depth understanding of the target application’s internal API, database schema, keystore, and file-vault structure.
ReliaQuest notes that the discovered resource is an application-specific variation of the Clop ransomware group’s known mass exploitation framework. The web shell was linked to the Clop ransomware group because of extortion e-mails sent by the threat actors using the e-mail addresses associated with the data-leakage web site operated by Clop.
In addition, the researchers identified X-windchill-req headers used by the web shell, which were also used by the Clop ransomware group in the past, as well as similar tactics, techniques, and procedures (TTPs). Earlier this year, Clop ransomware group’s infrastructure was found to target enterprise business software solutions such as Accellion FTA, GoAnywhere MFT, SolarWinds Serv-U FTP, Cleo, and MOVEit Transfer. This campaign, which affected the MOVEit Transfer application, compromised more than 2,770 organizations worldwide.
The web shell is implemented as JavaServer Pages (JSP), which directly imports the PTC Windchill-specific classes such as MethodContext, WTConnection, and WTKeyStoreUtil, giving the threat actors’ access to PTC Windchill’s native functions, including the database, encrypted credentials decryption, and locating files stored in the application’s vaults.
The web shell’s command execution capability was established using the custom protocol that utilizes the HTTP X-windchill-req header.
Overall, the custom component allowed the attackers to achieve multiple malicious objectives, including Windchill secrets and configuration data theft, file vault discovery and enumeration, directory listing, file retrieval and deletion, executing additional Java classes, and identifying the server’s operating system.
Besides that, ReliaQuest reports that the web shell’s implementation contains the Windchill vault enumeration code that queries multiple Windchill database tables, namely ApplicationData, FVITEM, FVMOUNT, and MasteredOnReplicaItem.
The PTC released a set of security updates to address CVE-2026-12569 on June 17. Additionally, the vulnerability was included in the CISA’s Known Exploited Vulnerabilities catalog earlier this week after the PTC reported active exploitation attempts in the wild. Ransom-ISAC confirmed that ransomware group Clop was behind the attacks by sending extortion emails to the employees of the targeted organizations.
ReliaQuest recommends that all the JSP files found in the PTC Windchill directories should be investigated for any suspicious content and that the researchers should look for the X-windchill-req string.
Moreover, the organizations that determined that their Windchill servers were compromised by the ransomware group should change the LDAP manager’s password and other user credentials because they are considered insecure and may have been leaked.
