CVE-2025-63708 is a Cross-Site Scripting (XSS) vulnerability identified in the SourceCodester AI Font Matcher application, specifically within its webfonts API handling mechanism. The root cause is the failure to properly sanitize font family names before processing them. Attackers can exploit this by intercepting fetch requests to the webfonts endpoint and injecting malicious JavaScript payloads disguised as font data. When a victim's browser processes this malicious font data, the injected script executes in the context of the vulnerable web application. This execution can lead to theft of session cookies, enabling account hijacking, and allow attackers to perform unauthorized actions on behalf of authenticated users. The vulnerability does not require prior authentication and can be triggered remotely, increasing its risk profile. Although no CVSS score has been assigned and no known exploits are reported in the wild, the vulnerability's nature suggests a significant threat. The lack of proper input validation and sanitization in font family names is a critical oversight, as font APIs are commonly used in modern web applications to enhance UI/UX. The attack vector leverages the browser's trust in font resources, making detection and prevention challenging without proper security controls. This vulnerability highlights the importance of securing all input vectors, including those less commonly considered like font names, to prevent script injection attacks.

For European organizations, this vulnerability poses a substantial risk to web applications that utilize the SourceCodester AI Font Matcher or similar font handling APIs. The primary impact is on the confidentiality and integrity of user sessions, as attackers can steal session cookies and hijack accounts. This can lead to unauthorized access to sensitive data, manipulation of user actions, and potential lateral movement within affected systems. Organizations in sectors such as finance, healthcare, and e-commerce, which rely heavily on web applications for customer interaction, are particularly vulnerable. The exploitation could result in data breaches, financial loss, reputational damage, and regulatory penalties under GDPR due to compromised personal data. Additionally, the vulnerability could be leveraged as an initial foothold for more complex attacks, including phishing campaigns or malware distribution. The remote and unauthenticated nature of the exploit increases the attack surface, making it easier for threat actors to target multiple organizations simultaneously. The absence of known exploits in the wild currently limits immediate widespread impact but does not diminish the potential severity once exploitation techniques become publicly available.

To mitigate CVE-2025-63708, organizations should implement strict input validation and sanitization on all font family name inputs within the webfonts API to prevent injection of malicious scripts. Employing a robust Content Security Policy (CSP) that restricts the execution of inline scripts and limits sources for fonts and scripts can significantly reduce exploitation risk. Monitoring and logging fetch requests to the webfonts endpoint for unusual or unexpected payloads can help detect attempted exploitation. Web application firewalls (WAFs) should be configured to identify and block suspicious requests targeting font APIs. Developers should review and update the SourceCodester AI Font Matcher to the latest patched version once available, or apply custom patches to sanitize inputs. Additionally, educating developers about securing less obvious input vectors like font names is critical. Regular security assessments and penetration testing focusing on client-side injection vectors will help identify similar vulnerabilities. Finally, organizations should ensure that user sessions are protected with secure cookie attributes (HttpOnly, Secure, SameSite) to limit the impact of session theft.