CVE-2025-59838 identifies a cross-site scripting (XSS) vulnerability in Monkeytype, a minimalistic and customizable typing test application. The vulnerability is classified under CWE-79, indicating improper neutralization of input during web page generation. Specifically, in versions 25.36.0 and earlier, the application fails to properly sanitize user-supplied input when loading saved custom texts, which can be manipulated to include malicious JavaScript code. This flaw allows an attacker with limited privileges (local access with low privileges) to craft a specially formed saved text that, when loaded by a user, executes arbitrary scripts in the context of the victim's browser session. The vulnerability requires user interaction to trigger and does not affect the confidentiality, integrity, or availability of the system beyond the session scope. The CVSS 4.0 base score is 2.4, reflecting the low severity due to the attack vector being local (AV:L), requiring user interaction (UI:P), and low privileges (PR:L). The vulnerability was published on September 25, 2025, and has been fixed in Monkeytype version 25.44.0. No known exploits have been reported in the wild, reducing immediate risk. However, the vulnerability could be leveraged in targeted scenarios where attackers have access to user environments and can trick users into loading malicious saved texts, potentially leading to session hijacking or phishing within the application context.

For European organizations, the impact of CVE-2025-59838 is relatively limited due to the low severity and the requirement for local access and user interaction. Organizations using Monkeytype primarily for employee training, educational purposes, or typing skill assessments may face risks of session-based attacks if users load malicious saved custom texts. Potential impacts include execution of arbitrary scripts in the user's browser, which could lead to session hijacking, phishing, or theft of session cookies within the application context. However, since Monkeytype is a niche application and the vulnerability does not allow remote exploitation or privilege escalation, the broader organizational impact is minimal. Nevertheless, organizations should consider the risk in environments where Monkeytype is widely used, especially in sectors with high security requirements or where user workstations are shared or less controlled. Failure to patch could allow attackers with local access to conduct targeted attacks against users, potentially undermining trust in training platforms or leading to minor data exposure within the application session.

To mitigate CVE-2025-59838, European organizations should immediately update Monkeytype to version 25.44.0 or later, where the vulnerability has been fixed. Additionally, organizations should implement strict controls on the use of saved custom texts, including restricting the ability to import or load such texts from untrusted sources. User education is critical to prevent loading suspicious or unsolicited saved texts. Employing endpoint security solutions that monitor and restrict script execution in browsers can provide an additional layer of defense. Organizations should also review and enforce least privilege principles to limit local access rights, reducing the risk of exploitation. Regularly auditing installed software versions and applying timely patches will help prevent exploitation of similar vulnerabilities. Finally, monitoring user activity for unusual behavior related to Monkeytype usage may help detect attempted exploitation.