Description

Contributor Arbitrary File Upload in Sync Post With Other Site <= 1.9.3 versions.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "9.9",
  "pubDate": "2026-08-18T14:17:03.400Z",
  "pubdate": "2026-08-18T14:17:03.400Z",
  "executiveSummary": "An arbitrary file upload vulnerability has been identified in the Sync Post With Other Site plugin affecting versions <= 1.9.3. This security flaw enables authenticated users with contributor-level privileges or higher to upload arbitrary files to the underlying web server hosting the affected WordPress installation.\nThe primary impact of this vulnerability is potential remote code execution and full system compromise. By leveraging restricted file upload mechanics improperly validated by the vulnerable component, an attacker can upload malicious payloads, such as web shells, directly into accessible directories on the server.\nThe affected product is the Sync Post With Other Site plugin across all versions up to and including 1.9.3. The risk implications are critical, as successful exploitation bypasses intended restrictions on file type verification, allowing low-privileged contributors to execute arbitrary code within the context of the web server user.\nAttacker capabilities require authenticated access to the target application with at least contributor privileges. Exploitation requirements involve interacting with the vulnerable post-synchronization or file handling functionality provided by the plugin to upload and subsequently trigger the malicious payload.",
  "technicalDetails": "The vulnerability resides within the file processing and synchronization mechanisms of the Sync Post With Other Site plugin in versions <= 1.9.3. The root cause stems from insufficient validation and sanitization of user-supplied files during upload operations, lacking strict enforcement of allowed MIME types, file extensions, and destination path controls.\nAuthentication and privilege requirements necessitate that the malicious actor holds at least contributor-level access within the target WordPress environment. Although contributors typically lack the capability to upload arbitrary files or media in default configurations, flaws in the plugin's authorization checks or input handling bypass these security boundaries.\nThe attack flow proceeds in a sequential manner. First, an attacker authenticates as a contributor and crafts a malicious HTTP POST request targeting the vulnerable component within the Sync Post With Other Site plugin. This request includes a multipart payload containing an executable file disguised or improperly filtered by the application logic.\nUpon receiving the request, the vulnerable component fails to adequately verify the safety of the uploaded file. Consequently, the application writes the arbitrary file to the web server's file system without proper sanitization or renaming protections. The network exposure is standard HTTP/HTTPS, accessible wherever the web application is reachable.\nPost-exploitation impact involves the execution of the uploaded payload. Because the file is written to a web-accessible directory, the attacker can directly issue subsequent HTTP requests to the uploaded file path, triggering execution via the server's script processor. This leads to arbitrary command execution, potential lateral movement, data exfiltration, or complete administrative takeover of the affected WordPress site."
}