Description

Unauthenticated Cross Site Scripting (XSS) in Ninja Forms File Uploads Extension <= 3.3.26 versions.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "7.1",
  "pubDate": "2026-09-03T17:17:24.533Z",
  "pubdate": "2026-09-03T17:17:24.533Z",
  "executiveSummary": "The Ninja Forms File Uploads extension, in versions 3.3.26 and below, is susceptible to an unauthenticated Stored Cross-Site Scripting (XSS) vulnerability. This security flaw stems from the improper sanitization of user-supplied input during the file upload process, allowing an unauthenticated attacker to inject malicious JavaScript payloads. The vulnerability resides within the way the extension handles file metadata or naming conventions before rendering them in the administrative or public-facing dashboards. Successful exploitation allows for the execution of arbitrary scripts within the context of the victim's browser session. The risk implications are severe, as an attacker could potentially hijack administrative sessions, steal sensitive cookies, or perform unauthorized actions on behalf of the victim. Because this vulnerability does not require authentication, it significantly lowers the barrier for entry for threat actors, as the attack can be initiated by any user capable of interacting with the form submission process. Mitigation requires an immediate update to the latest patched version of the Ninja Forms File Uploads extension to ensure that input validation and output encoding are properly enforced.",
  "technicalDetails": "The vulnerability is classified as a Stored Cross-Site Scripting (XSS) flaw located within the file handling logic of the Ninja Forms File Uploads extension. The root cause is the failure to adequately sanitize or encode user-supplied data associated with uploaded files, specifically within filenames or metadata fields processed by the extension. When a user uploads a file, the plugin processes the input; if an attacker crafts a filename containing malicious JavaScript payloads—such as <script>alert('XSS')</script>—the plugin fails to neutralize these tags before persisting them into the database or rendering them in the administrative interface.\nThe attack flow begins when an unauthenticated actor identifies a page or post containing an active Ninja Forms submission form that includes the vulnerable File Uploads component. The attacker initiates a multipart/form-data upload request, substituting the standard filename for a malicious payload. Because the server-side processing logic lacks sufficient input validation and context-aware output encoding, the script is stored directly within the WordPress database. When an administrator or another user accesses the Ninja Forms submissions panel to review the uploaded content, the application renders the malicious filename in the browser. Consequently, the browser executes the injected script as if it were legitimate code originating from the trusted origin.\nThis vulnerability is particularly dangerous because it operates in the context of the WordPress administrative session. The payload executes with the privileges of the victim user viewing the entry. If the victim is an administrator, the attacker can leverage the XSS to perform unauthorized actions, such as creating new administrative users, modifying plugin settings, or exfiltrating sensitive site data. The lack of authentication requirements means that any actor with network access to the submission form can trigger this injection. The attack is persistent, meaning the malicious payload remains stored and will execute every time an authorized user interacts with the compromised submission entry, providing a long-term mechanism for session persistence and control. The vulnerable component is the File Uploads extension's input processing module, which fails to enforce strict character filtering or use appropriate escaping functions, such as esc_html() or sanitize_file_name(), when displaying uploaded data in the WordPress backend."
}