CVE-2025-58353 is a high-severity cross-site scripting (XSS) vulnerability affecting all versions of the Promptcraft Forge Studio toolkit, developed by MarceloTessaro. This toolkit is used for evaluating, optimizing, and maintaining large language model (LLM)-powered applications. The vulnerability arises from improper input sanitization during web page generation. Specifically, the product attempts to sanitize user input by applying regex-based blacklists, such as replacing occurrences of 'javascript:' with an empty string using the pattern replace(/javascript:/gi, ''). However, the sanitization logic only applies each replacement once and uses multi-character tokens, which can lead to overlapping token issues. This means that removing one dangerous token can inadvertently create a new executable token in the input string. As a result, the sanitized input may still contain executable payloads when injected into HTML attributes like href or src or directly into the DOM, enabling an attacker to execute arbitrary JavaScript code in the context of the victim's browser. The vulnerability is classified under CWE-79 (Improper Neutralization of Input During Web Page Generation), CWE-20 (Improper Input Validation), and CWE-184 (Incomplete Blacklist). The CVSS v3.1 base score is 8.2, indicating a high severity level. The vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:L/A:N indicates that the attack can be performed remotely over the network without privileges, requires low attack complexity, no privileges, but requires user interaction (such as clicking a crafted link). The vulnerability impacts confidentiality heavily, with limited impact on integrity and no impact on availability. Currently, there is no available patch or fix for this vulnerability, and no known exploits have been reported in the wild. This leaves users of Promptcraft Forge Studio exposed to potential XSS attacks that could lead to session hijacking, data theft, or other malicious activities through client-side script execution.

For European organizations using Promptcraft Forge Studio, this vulnerability poses a significant risk, especially for those integrating LLM-powered applications into their web environments. Successful exploitation could allow attackers to execute arbitrary JavaScript in the context of users’ browsers, potentially leading to theft of sensitive information such as authentication tokens, personal data, or intellectual property. This could also facilitate phishing attacks or the spread of malware within corporate networks. Given the high confidentiality impact, organizations handling sensitive or regulated data (e.g., GDPR-protected personal data) face compliance risks and potential legal consequences if breaches occur. The requirement for user interaction means social engineering or targeted phishing campaigns could be used to trigger the exploit. The lack of a fix increases the urgency for organizations to implement compensating controls. Additionally, since the vulnerability affects the core input sanitization logic, any web-facing component or internal tool relying on this package is at risk, potentially impacting development workflows and production environments.

1. Immediate mitigation should focus on disabling or restricting the use of Promptcraft Forge Studio in production environments until a patch is available. 2. Employ Content Security Policy (CSP) headers with strict script-src directives to limit the execution of unauthorized scripts in affected web applications. 3. Implement additional server-side input validation and sanitization using well-established libraries that do not rely solely on regex blacklists, such as OWASP Java Encoder or DOMPurify for JavaScript. 4. Educate users and developers about the risks of clicking untrusted links or interacting with unverified content to reduce the likelihood of successful user interaction exploitation. 5. Monitor web application logs and network traffic for suspicious activities indicative of XSS attempts, such as unusual query parameters or script injections. 6. Consider isolating or sandboxing components that use Promptcraft Forge Studio to limit the scope of potential exploitation. 7. Engage with the vendor or open-source community to track the development of a fix and apply patches promptly once available. 8. For organizations with mature security operations, deploy web application firewalls (WAFs) with custom rules to detect and block payloads exploiting this specific XSS pattern.