CVE-2025-50049 is a Stored Cross-site Scripting (XSS) vulnerability classified under CWE-79, affecting the product Modern Footnotes developed by prismtechstudios. This vulnerability arises due to improper neutralization of input during web page generation, allowing malicious scripts to be stored and subsequently executed in the context of users' browsers when they access affected pages. The vulnerability impacts versions up to 1.4.19 of Modern Footnotes. The CVSS v3.1 base score is 6.5, indicating a medium severity level. The vector string (CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:L) reveals that the attack can be executed remotely over the network (AV:N) with low attack complexity (AC:L), but requires the attacker to have some privileges (PR:L) and user interaction (UI:R). The scope is changed (S:C), meaning the vulnerability affects resources beyond the initially vulnerable component. The impact affects confidentiality, integrity, and availability at a low level (C:L, I:L, A:L). Stored XSS vulnerabilities can lead to session hijacking, credential theft, defacement, or distribution of malware, depending on the context in which the malicious script executes. Although no known exploits are reported in the wild yet, the presence of stored XSS in a web-based product that likely integrates into content management or documentation workflows poses a significant risk, especially if deployed in environments with multiple users or sensitive data. The lack of available patches at the time of publication increases the urgency for mitigation and monitoring.

For European organizations, the impact of this vulnerability can be significant, particularly for those using Modern Footnotes in their web applications, intranets, or documentation portals. Stored XSS can lead to unauthorized access to user sessions, data leakage, and potential compromise of internal systems if administrative users are targeted. Organizations in sectors such as finance, healthcare, government, and critical infrastructure are especially at risk due to the sensitivity of their data and regulatory requirements like GDPR. The vulnerability's ability to affect confidentiality, integrity, and availability, even at low levels, can result in reputational damage, regulatory fines, and operational disruptions. Furthermore, the requirement for user interaction means phishing or social engineering could be used to trigger the exploit, increasing the attack surface. The changed scope indicates that the vulnerability could impact components beyond the immediate application, potentially affecting integrated systems or services. Given the interconnected nature of European IT environments, lateral movement or cascading effects cannot be ruled out if exploited.

1. Immediate mitigation should include disabling or restricting the use of Modern Footnotes in environments where untrusted input is accepted until a patch is available. 2. Implement strict input validation and output encoding on all user-supplied data within the application, focusing on HTML context encoding to prevent script injection. 3. Employ Content Security Policy (CSP) headers with restrictive script-src directives to limit the execution of unauthorized scripts. 4. Conduct thorough code reviews and penetration testing focused on XSS vectors in the affected application and any integrated systems. 5. Educate users, especially those with privileges, about the risks of interacting with untrusted content and phishing attempts that could trigger stored XSS payloads. 6. Monitor web application logs and user activity for unusual behavior indicative of exploitation attempts. 7. Where possible, isolate the Modern Footnotes application within segmented network zones to limit potential lateral movement. 8. Stay alert for vendor updates or patches and apply them promptly once available. 9. Consider deploying Web Application Firewalls (WAFs) with custom rules to detect and block common XSS payloads targeting this product.