CVE-2025-57963 is a Cross-site Scripting (XSS) vulnerability classified under CWE-79, specifically a DOM-Based XSS issue affecting Zoho Subscriptions' Zoho Billing product. This vulnerability arises from improper neutralization of input during web page generation, allowing malicious scripts to be executed in the context of a user's browser. The affected versions include all versions up to 4.1, with no specific lower bound version identified. The vulnerability enables an attacker to inject and execute arbitrary JavaScript code by manipulating client-side scripts that handle user input without proper sanitization or encoding. Exploitation requires the attacker to lure an authenticated user with at least low privileges (PR:L) into interacting with a crafted URL or payload (UI:R), which then triggers the malicious script execution. The vulnerability has a CVSS v3.1 base score of 6.5, indicating a medium severity level. The vector details (AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:L) show that the attack can be performed remotely over the network with low attack complexity, requires privileges but only low-level user rights, and user interaction is necessary. The scope is changed (S:C), meaning the vulnerability affects resources beyond the initially vulnerable component. The impact affects confidentiality, integrity, and availability to a limited extent (L). No known exploits are currently reported in the wild, and no patches or fixes have been linked yet. The vulnerability is significant because Zoho Billing is a subscription and billing management platform used by businesses to handle invoicing, payments, and customer subscriptions, making it a valuable target for attackers aiming to compromise business operations or steal sensitive customer data via session hijacking or credential theft through XSS attacks.

For European organizations using Zoho Billing, this vulnerability poses a risk of client-side script injection that can lead to session hijacking, theft of sensitive billing and customer data, or manipulation of billing information. Given the nature of the product, attackers could exploit this vulnerability to impersonate legitimate users, potentially leading to fraudulent transactions or unauthorized access to subscription management features. The medium severity score reflects that while the impact on confidentiality, integrity, and availability is limited, the scope change means that the attack could affect multiple components or users beyond the initial vulnerable interface. European businesses relying on Zoho Billing for financial operations could face reputational damage, regulatory compliance issues under GDPR if personal data is compromised, and financial losses. The requirement for user interaction and low privileges reduces the likelihood of widespread automated exploitation but does not eliminate targeted attacks, especially against employees with access to the billing system. The absence of known exploits in the wild currently limits immediate risk but organizations should remain vigilant given the public disclosure.

1. Immediate mitigation should include educating users and administrators about the risk of phishing or social engineering attacks that could deliver malicious payloads exploiting this XSS vulnerability. 2. Implement strict Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts and reduce the impact of DOM-based XSS. 3. Employ input validation and output encoding on all user-controllable inputs within the Zoho Billing interface, especially those reflected in the DOM, to prevent script injection. 4. Monitor and restrict user privileges to the minimum necessary to reduce the impact of exploitation requiring low privileges. 5. Regularly audit and review client-side scripts for unsafe DOM manipulations and update or patch the Zoho Billing product as soon as vendor fixes become available. 6. Use web application firewalls (WAFs) with rules tailored to detect and block XSS attack patterns targeting Zoho Billing. 7. Conduct internal penetration testing focusing on DOM-based XSS vectors to identify and remediate any additional weaknesses. 8. Maintain up-to-date backups and incident response plans to quickly recover from any successful exploitation.