CVE-2025-59549 is a medium-severity vulnerability classified as CWE-79, which corresponds to Improper Neutralization of Input During Web Page Generation, commonly known as Cross-site Scripting (XSS). This vulnerability affects the fatcatapps GetResponse Forms product, specifically all versions up to and including 2.6.0. The issue allows an attacker to inject malicious scripts that are stored persistently within the application and subsequently executed in the context of users' browsers when they access the affected forms. The vulnerability arises because user input is not properly sanitized or encoded before being embedded into web pages generated by the application. According to the CVSS 3.1 vector (AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:L), the attack can be launched remotely over the network with low attack complexity, but requires the attacker to have some level of privileges (PR:L) and user interaction (UI:R) to trigger the exploit. The scope is changed (S:C), indicating that the vulnerability affects resources beyond the initially vulnerable component. The impact includes limited confidentiality, integrity, and availability losses, as the attacker can execute arbitrary scripts that may steal session tokens, manipulate displayed content, or disrupt service availability. No known exploits are reported in the wild yet, and no patches are currently linked, which suggests that organizations using this product should prioritize mitigation and monitoring. Stored XSS vulnerabilities are particularly dangerous because they can affect multiple users and persist over time, increasing the risk of widespread compromise or phishing attacks leveraging the trusted site context.

For European organizations, the impact of this vulnerability can be significant, especially for those relying on GetResponse Forms for customer engagement, lead generation, or internal workflows. Exploitation could lead to theft of sensitive user data, including personal information protected under GDPR, resulting in regulatory penalties and reputational damage. The ability to execute scripts in users' browsers could facilitate session hijacking, unauthorized actions on behalf of users, or distribution of malware. This is particularly critical for organizations in sectors such as finance, healthcare, and e-commerce, where trust and data integrity are paramount. Additionally, the cross-site scripting vulnerability could be leveraged in targeted phishing campaigns against European users, exploiting localized language and cultural context to increase success rates. The medium CVSS score reflects a moderate but non-negligible risk, emphasizing the need for timely remediation to prevent escalation or chaining with other vulnerabilities.

Organizations should implement a multi-layered mitigation approach beyond generic advice: 1) Immediately audit and sanitize all user-generated content submitted through GetResponse Forms to ensure proper encoding and filtering of HTML and script tags. 2) Employ Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts and reduce the impact of potential XSS payloads. 3) Monitor application logs and user activity for unusual patterns indicative of attempted exploitation, such as unexpected script injections or anomalous form submissions. 4) Restrict privileges required to submit or manage forms to minimize the attack surface, as the vulnerability requires some level of privilege. 5) Engage with fatcatapps for updates or patches and apply them promptly once available. 6) Educate users about the risks of interacting with suspicious links or forms, emphasizing the need for caution with unexpected requests. 7) Consider implementing web application firewalls (WAF) with rules tailored to detect and block XSS attempts targeting GetResponse Forms. 8) Conduct regular security assessments and penetration testing focused on input validation and output encoding within the affected application components.