CVE-2026-53592 in FreeScout
Summary
by MITRE • 07/20/2026
FreeScout is a free help desk and shared inbox built with PHP's Laravel framework. A Prototype Pollution condition in the `getQueryParam` function `/public/js/main.js` and was addressed in version 1.8.139 by blocking URL query keys matching the pattern `__proto__`. However, this mitigation is incomplete: it only filters top-level `__proto__` keys and fails to sanitize nested forms such as `b[__proto__][polluted]=PWNED`. As a result, an attacker-controlled URL query string can still write into `Object.prototype` on any page that loads `main.js`. Version 1.8.223 contains a updated fix.
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Analysis
by VulDB Data Team • 07/20/2026
The vulnerability in FreeScout represents a prototype pollution flaw that emerged from the application's handling of URL query parameters within its JavaScript frontend component. This issue stems from the `getQueryParam` function located in `/public/js/main.js`, which processes user-supplied input without proper sanitization mechanisms. The flaw allows attackers to manipulate object prototypes through carefully crafted query strings, enabling them to inject malicious properties into the global Object prototype that affects all subsequent object operations within the application's runtime environment.
The technical implementation of this vulnerability demonstrates a classic prototype pollution attack vector where the initial mitigation approach proved insufficient due to incomplete sanitization logic. The original fix in version 1.8.139 only addressed direct top-level `_proto_` key injection but failed to account for nested property access patterns that can bypass simple string matching filters. This oversight creates a pathway for attackers to utilize complex query structures such as `b[_proto_][polluted]=PWNED` where the pollution occurs at multiple levels of object hierarchy, effectively circumventing the protection mechanism designed to block prototype manipulation.
The operational impact of this vulnerability extends beyond typical cross-site scripting scenarios and represents a fundamental threat to application integrity. When an attacker successfully pollutes the Object.prototype through nested query parameters, they can potentially influence how JavaScript objects behave throughout the entire application lifecycle. This affects any page that loads the vulnerable `main.js` file, making it a widespread concern across the entire FreeScout interface. The attack surface becomes particularly dangerous because prototype pollution can enable various downstream attacks including but not limited to denial of service conditions, data manipulation, and in some cases, arbitrary code execution depending on how the application processes these polluted objects.
The remediation implemented in version 1.8.223 represents a more comprehensive approach to addressing the prototype pollution vulnerability by expanding the sanitization scope beyond simple string matching. This updated fix properly handles nested property access patterns that could previously bypass the original filtering mechanism, thereby providing complete protection against prototype pollution attacks. The evolution from version 1.8.139 to 1.8.223 demonstrates the importance of thorough vulnerability assessment and the necessity of considering all possible attack vectors when implementing security mitigations.
This vulnerability aligns with CWE-471, which specifically addresses the insertion of data into a prototype object without proper validation or sanitization, and relates to ATT&CK technique T1059.007 for JavaScript-based command execution through manipulated object properties. Organizations using FreeScout should prioritize immediate upgrade to version 1.8.223 or later to ensure complete protection against this class of prototype pollution attacks that could compromise application integrity and user data confidentiality.