CVE-2025-50938 is a cross-site scripting (XSS) vulnerability identified in the Hustoj platform, specifically exploitable via the TID parameter in the thread.php script. Hustoj is an open-source online judge system commonly used in programming contest environments to automatically evaluate submitted code. The vulnerability allows an attacker to inject malicious scripts into the web application by manipulating the TID parameter, which is likely used to identify threads or discussion topics within the platform. When a victim user accesses a crafted URL containing the malicious payload, the injected script executes in the context of the victim's browser session. This can lead to session hijacking, theft of authentication tokens, defacement, or redirection to malicious sites. The vulnerability is categorized as a reflected or stored XSS depending on how the TID parameter is processed and rendered. No specific affected versions are listed, and no patch or exploit details are currently available, indicating that the vulnerability is newly published and may not yet be widely exploited. The absence of a CVSS score suggests that the vulnerability has not been fully assessed for impact or exploitability. However, XSS vulnerabilities generally pose significant risks to web applications that handle user sessions and sensitive data. The vulnerability's presence in Hustoj, a platform used in educational and competitive programming contexts, could allow attackers to compromise user accounts or disrupt contest operations if exploited.

For European organizations, especially educational institutions, universities, and competitive programming platforms that deploy Hustoj, this vulnerability could have several impacts. Confidentiality may be compromised if attackers steal session cookies or authentication tokens, leading to unauthorized access to user accounts and potentially sensitive contest data or user information. Integrity could be affected if attackers inject misleading or malicious content into contest threads or discussions, undermining trust in the platform. Availability might be indirectly impacted if attacks lead to denial of service through script-based disruptions or if administrators disable the platform to mitigate risks. Given the collaborative and competitive nature of Hustoj deployments, exploitation could disrupt contest fairness and user trust. Furthermore, the vulnerability could be leveraged as a foothold for further attacks within the hosting environment if combined with other vulnerabilities. The lack of known exploits in the wild currently reduces immediate risk but does not eliminate the potential for targeted attacks, especially in high-value environments.

To mitigate this vulnerability, European organizations using Hustoj should immediately review and sanitize all user-supplied input, particularly the TID parameter in thread.php, to ensure that it does not allow injection of executable scripts. Implementing strict input validation and output encoding consistent with OWASP XSS prevention guidelines is critical. Organizations should monitor for updates or patches from Hustoj maintainers and apply them promptly once available. In the interim, deploying web application firewalls (WAFs) with rules to detect and block XSS payloads targeting the TID parameter can reduce risk. Additionally, enabling Content Security Policy (CSP) headers can limit the impact of any injected scripts by restricting script execution sources. Regular security assessments and penetration testing focused on web application inputs should be conducted to identify similar vulnerabilities. User education on phishing risks related to XSS attacks can also help mitigate social engineering attempts leveraging this vulnerability.