CVE-2026-59666 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 “nomOrigen” parameter is affected – endpoint “/es/origins/store”.
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Analysis
by VulDB Data Team • 10/02/2026
The identified security flaw represents a classic Cross-Site Scripting, commonly referred to as XSS, vulnerability within the Repasat web application architecture. This specific weakness resides in the handling of user-supplied input for the nomOrigen parameter during data submission operations targeting the /es/origins/store endpoint. The fundamental nature of this defect lies in the insufficient sanitization or validation of external data before it is processed by the server and subsequently reflected back to client-side browsers without proper encoding. When an attacker crafts a malicious payload containing executable JavaScript code, they can inject this script into the application's response stream. Because the application fails to neutralize special characters that have semantic meaning in HTML contexts, such as angle brackets or quotation marks, the browser interprets the injected content not merely as text but as active script instructions. This failure aligns directly with CWE-79, which categorizes improper neutralization of input during web page generation, highlighting a critical lapse in secure coding practices regarding output encoding and input validation mechanisms.
The operational impact of exploiting this vulnerability is severe, primarily because it enables an attacker to execute arbitrary code within the context of the victim’s browser session. By tricking a user into accessing a specially crafted URL or interacting with a compromised page that triggers the vulnerable endpoint, the attacker can achieve remote code execution on the client side. This capability allows for a wide range of malicious activities including but not limited to stealing sensitive cookies and authentication tokens, hijacking active sessions, performing actions on behalf of the victim such as modifying account settings or submitting fraudulent forms, and defacing the user interface. The attack vector is typically classified under remote exploitation with low complexity, requiring only social engineering elements like phishing links rather than complex network-level exploits. This aligns with MITRE ATT&CK technique T1059, specifically sub-technique 007 for JavaScript execution, which describes how adversaries use browser-based scripts to achieve their objectives without deploying native binaries that might trigger endpoint detection systems.
From a defensive perspective, mitigating this vulnerability requires a multi-layered approach focusing on both input validation and output encoding. The most effective immediate remedy is implementing strict context-aware output encoding for the nomOrigen parameter whenever it is rendered in HTML responses. This involves converting special characters into their corresponding HTML entities so that browsers treat them as literal text rather than executable code. Additionally, developers should enforce rigorous server-side input validation to ensure that only expected data types and formats are accepted by the /es/origins/store endpoint, rejecting any content containing script tags or event handlers. Implementing a Content Security Policy header can further mitigate the impact of successful XSS attacks by restricting the sources from which scripts can be loaded and executed within the application domain. Long-term remediation should involve adopting secure coding frameworks that automatically handle encoding and integrating static analysis tools into the development pipeline to detect such flaws before deployment. Regular security audits and penetration testing are also essential to identify similar weaknesses across other parameters and endpoints, ensuring a robust defense against client-side injection attacks.