CVE-2026-100179 in Calculated Fields Form Plugin
Summary
by MITRE • 10/01/2026
The Calculated Fields Form – AI Form Builder for WordPress – Contact, Payment, Quote, Quiz & More plugin for WordPress is vulnerable to Reflected DOM-Based Cross-Site Scripting via the 'x (any URL parameter consumed by the form's calculated equation)' parameter in all versions up to, and including, 5.5.1.3 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that execute if they can successfully trick a user into performing an action such as clicking on a link. Exploitation requires the target site to have a public form configured with a Select2-enabled dropdown whose choices are populated via a calculated equation that pipes a URL parameter through GETURLPARAMETER() into setChoices({texts:[...]}); given that configuration, exploitation requires only a single crafted link.
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Analysis
by VulDB Data Team • 10/01/2026
The Calculated Fields Form plugin for WordPress, specifically versions up to and including 5.5.1.3, contains a critical security flaw classified as a Reflected DOM-Based Cross-Site Scripting vulnerability. This issue stems from insufficient input sanitization and output escaping mechanisms within the application's handling of URL parameters that are consumed by calculated equations. The core technical failure occurs when user-supplied data is passed directly into JavaScript execution contexts without adequate validation, allowing malicious scripts to be injected into web pages served to users.
The vulnerability specifically targets forms configured with a Select2-enabled dropdown where choices are dynamically populated via a calculated equation. In this configuration, the plugin utilizes the GETURLPARAMETER() function to pipe URL parameters into setChoices({texts:[...]}). Because the input is not properly sanitized or escaped before being processed by the JavaScript engine on the client side, an attacker can inject arbitrary web scripts. This represents a classic case of untrusted data reaching a sink that executes code, which aligns with CWE-79 in terms of improper neutralization of input during web page generation and CWE-83 regarding cross-site scripting via DOM methods.
From an operational perspective, this vulnerability allows unauthenticated attackers to execute arbitrary JavaScript in the context of the victim's browser session. Exploitation does not require prior authentication or complex multi-step attacks; it relies on social engineering tactics such as tricking a user into clicking a crafted link containing malicious payload data within URL parameters. Once executed, the injected script can perform various malicious actions including stealing session cookies, hijacking user sessions, performing unauthorized actions on behalf of the victim, or redirecting users to phishing sites. This significantly compromises the confidentiality and integrity of interactions with the WordPress site hosting the vulnerable form.
The attack vector is categorized under MITRE ATT&CK technique T1059.007, which covers JavaScript-based execution, specifically within the context of client-side code injection. The reflection aspect means that the malicious payload is immediately returned to the user in an HTTP response without being stored on the server, distinguishing it from persistent XSS attacks but still posing a severe risk due to its ease of exploitation through simple link sharing or embedding in emails and other web pages.
To mitigate this vulnerability, administrators should update the Calculated Fields Form plugin to version 5.5.1.4 or later where these sanitization issues have been addressed. Until an upgrade is possible, it is advisable to disable any forms that utilize Select2 dropdowns populated via calculated equations with URL parameters if such functionality is not strictly required. Additionally, implementing a Web Application Firewall can provide some protection by filtering out known malicious patterns in query strings before they reach the application logic. Regular security audits and code reviews focusing on input validation and output encoding practices are essential to prevent similar DOM-based XSS vulnerabilities in future development cycles.