CVE-2026-59663 in Repasat
Summary
by MITRE • 10/02/2026
Cross-Site Scripting vulnerability in the Repasat application. Successful exploitation of this vulnerability could allow an attacker to trick a user into executing arbitrary code in the victim’s browser. The “nomDelegacion” parameter is affected – endpoint “/es/delegations/store”.
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Analysis
by VulDB Data Team • 10/02/2026
The identified Cross-Site Scripting (XSS) vulnerability within the Repasat application represents a significant security risk that compromises the integrity and confidentiality of user interactions with the platform. This specific flaw resides in the handling of the nomDelegacion parameter during data submission to the /es/delegations/store endpoint. The core technical issue stems from insufficient input validation or improper output encoding, allowing an attacker to inject malicious client-side scripts into web pages viewed by other users. When a victim accesses a page containing this injected content, their browser executes the script in the context of the application’s domain, effectively bypassing same-origin policy restrictions that normally isolate different websites from each other.
From a technical perspective, this vulnerability falls under CWE-79, which classifies improper neutralization of input during web page generation as a critical weakness. The attacker can craft a malicious payload containing JavaScript code and trick an authenticated user into triggering the vulnerable endpoint or viewing a compromised page where the stored script is rendered. Because the parameter affects the /es/delegations/store endpoint, it suggests that the application may be storing this unsanitized input in its database for later retrieval and display to other users, characterizing this as a Stored XSS attack rather than a reflected one. This persistence amplifies the severity of the flaw, as each subsequent user viewing the affected content becomes a potential victim without needing further interaction from the attacker beyond the initial injection.
The operational impact of successfully exploiting this vulnerability is severe and multifaceted. An adversary can steal session cookies or authentication tokens, leading to account takeover and unauthorized access to sensitive administrative functions within Repasat. Furthermore, the attacker could perform actions on behalf of the victim, such as modifying delegation settings, deleting records, or altering configurations without authorization. In more advanced scenarios, the injected script could redirect users to phishing sites designed to harvest credentials or deploy malware onto the victim’s system through drive-by downloads if browser vulnerabilities are present. This undermines user trust and exposes the organization to regulatory penalties under data protection frameworks due to potential exposure of personal identifiable information.
To mitigate this vulnerability, immediate remediation efforts should focus on implementing robust input validation and output encoding strategies. All inputs received by the nomDelegacion parameter must be strictly validated against a whitelist of expected characters and formats before processing. When rendering user-supplied content in HTML contexts, developers must apply context-aware output encoding to ensure that special characters are escaped appropriately so they are treated as data rather than executable code. Additionally, implementing Content Security Policy headers can provide an additional layer of defense by restricting the sources from which scripts can be loaded and executed within the browser environment. Regular security testing using both static analysis tools and dynamic penetration tests is recommended to identify similar flaws across other endpoints in the application.
This vulnerability aligns with MITRE ATT&CK technique T1059, specifically sub-technique 007 for JavaScript execution, which describes how attackers use scripts embedded in web pages to compromise user sessions or perform unauthorized actions. Addressing this issue requires a comprehensive approach that includes not only fixing the specific code defect but also enhancing overall secure coding practices within the development lifecycle. By prioritizing input sanitization and adopting defense-in-depth strategies such as CSP implementation, organizations can significantly reduce their attack surface and protect users from malicious exploitation of client-side vulnerabilities in web applications like Repasat.