Description

The Forminator Forms WordPress plugin before 1.57.2.1 does not restrict which classes may be instantiated when it deserialises a value taken from an XML-RPC request, allowing users who hold its forms-management permission to write a file of their choosing and execute arbitrary code. That permission belongs to an administrator by default, and to any role the site has granted it through the Forminator Forms WordPress plugin before 1.57.2.1's own settings, so the issue is reachable well below administrator on sites that use that feature.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "8.5",
  "pubDate": "2026-09-20T07:16:50.430Z",
  "pubdate": "2026-09-20T07:16:50.430Z",
  "executiveSummary": "The Forminator Forms WordPress plugin (versions prior to 1.57.2.1) is affected by a critical insecure deserialization vulnerability within its XML-RPC request processing logic.\nThis vulnerability allows an authenticated attacker to perform arbitrary class instantiation, which can be leveraged to achieve arbitrary file write and subsequent remote code execution (RCE).\nThe issue stems from a lack of validation or filtering on object types during the deserialization of data supplied via XML-RPC requests.\nWhile the default configuration restricts access to administrative roles, the plugin's internal settings allow for the delegation of 'forms-management' permissions to lower-privileged users, significantly expanding the attack surface.\nSuccessful exploitation grants an attacker the ability to execute arbitrary commands on the underlying server, potentially leading to full site compromise and persistent unauthorized access.\nThis vulnerability poses a severe risk to the integrity, confidentiality, and availability of the affected WordPress environment.",
  "technicalDetails": "The root cause of this vulnerability is improper handling of serialized objects during the processing of XML-RPC requests in the Forminator Forms plugin. The plugin fails to implement a whitelist or any validation mechanism to restrict which classes may be instantiated when processing deserialized inputs.\nWhen the plugin deserializes a value provided in an XML-RPC request, an attacker can supply a crafted serialized payload that triggers the instantiation of unintended PHP classes. By selecting specific 'gadget' classes within the application or its dependencies, an attacker can manipulate the internal state of the application to execute secondary operations.\nThe attack flow proceeds as follows: First, the attacker identifies or gains the 'forms-management' permission required to interact with the vulnerable endpoint. Second, the attacker crafts a malicious serialized object payload designed to leverage existing PHP class structures that facilitate file system operations.\nThird, this payload is submitted to the XML-RPC endpoint. Upon reception, the plugin automatically deserializes the input without validation. The attacker-controlled object is instantiated, and via magic methods (such as __destruct, __wakeup, or __call), the attacker triggers the file write operation.\nBy overwriting a critical PHP file or uploading a new file in a web-accessible directory, the attacker achieves remote code execution. This allows the attacker to execute arbitrary system commands with the privileges of the web server user.\nThe vulnerability is accessible to any user granted 'forms-management' permissions. Because Forminator allows administrators to map this capability to custom or lower-privileged user roles, the potential for unauthorized exploitation extends beyond the administrator account.\nPost-exploitation impact includes full control over the WordPress instance, including database access, user credential harvesting, and the ability to pivot into the broader network infrastructure. The impact is critical as it bypasses standard input sanitization layers by targeting the underlying object instantiation logic within the PHP runtime environment."
}