The Solspace Freeform plugin for Craft CMS, a widely used form-building tool, suffers from a stored cross-site scripting (XSS) vulnerability identified as CVE-2026-26188. This vulnerability arises from improper neutralization of input during web page generation (CWE-79). Specifically, authenticated users with low privileges who can create or edit forms are able to inject arbitrary HTML or JavaScript code into form labels and integration metadata fields. These inputs are rendered in the Craft Control Panel's builder and integrations views using React's dangerouslySetInnerHTML property without adequate sanitization or encoding, allowing malicious scripts to be stored persistently. When an administrator or any user with higher privileges accesses these views, the injected scripts execute in their browser context, potentially leading to session hijacking, privilege escalation, or unauthorized actions within the CMS. The vulnerability affects all versions from 5.0.0 up to but not including 5.14.7, where the vendor has implemented proper input sanitization and output encoding to mitigate this risk. The CVSS 4.0 vector indicates network attack vector, low attack complexity, no privileges required beyond low-level authenticated access, and no user interaction needed beyond viewing the affected pages. Although no active exploits have been reported, the risk remains significant due to the potential impact on administrative accounts and the persistence of the injected payloads.

This vulnerability poses a moderate risk to organizations using the Solspace Freeform plugin on Craft CMS, particularly those with multiple user roles including low-privilege users and administrators. An attacker with low-level authenticated access can inject malicious scripts that execute in the context of higher-privileged users, such as administrators, leading to session hijacking, theft of sensitive information, unauthorized configuration changes, or deployment of further malware. This can compromise the integrity and confidentiality of the CMS environment and potentially the broader web infrastructure it supports. Since the vulnerability is stored XSS, the malicious payload persists and can affect multiple users over time. Organizations relying on Craft CMS for critical web applications or content management may face disruption, data breaches, or reputational damage if exploited. The medium CVSS score reflects the need for authentication and some user interaction (viewing the affected pages), which somewhat limits the attack surface but does not eliminate the threat. The absence of known exploits in the wild suggests that proactive patching can effectively prevent exploitation.

Organizations should immediately upgrade the Solspace Freeform plugin to version 5.14.7 or later, where this vulnerability is patched. Until upgrading is possible, restrict the ability to create or edit forms to trusted users only, minimizing the risk of malicious input injection. Implement additional Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts within the Craft Control Panel. Regularly audit form labels and integration metadata for suspicious or unexpected HTML/JavaScript content. Employ web application firewalls (WAFs) with custom rules to detect and block typical XSS payloads targeting the Craft Control Panel. Educate administrators to be cautious when reviewing forms or integration screens and to report anomalies promptly. Finally, monitor logs for unusual activity or access patterns that might indicate attempts to exploit this vulnerability.