CVE-2025-70458 identifies a DOM-based Cross-Site Scripting (XSS) vulnerability in the Sourcecodester Domain Availability Checker v1.0, specifically within the DomainCheckerApp class in the domain/script.js file. The vulnerability stems from the createResultElement method, which uses the unsafe innerHTML property to render domain search results based on user-supplied input. Because innerHTML directly injects HTML content into the DOM without proper sanitization or encoding, an attacker can craft malicious input that executes arbitrary JavaScript in the context of the victim's browser. This type of XSS is client-side and does not require server-side injection, making it exploitable via crafted URLs or input fields that reflect user data. The vulnerability does not require authentication but does require user interaction to trigger the malicious script execution. The CVSS 3.1 base score is 5.4, indicating medium severity, with an attack vector of network (remote), low attack complexity, no privileges required, user interaction required, and impacts limited confidentiality and integrity but no availability impact. No patches or known exploits have been reported yet. The underlying CWE is CWE-79, which covers improper neutralization of input leading to XSS. This vulnerability could be leveraged to steal cookies, session tokens, or perform actions on behalf of users, potentially leading to account compromise or data leakage in affected web applications using this component.

For European organizations, the impact of this vulnerability depends largely on the deployment of the Sourcecodester Domain Availability Checker or similar vulnerable components in their web infrastructure. If exploited, attackers could execute arbitrary scripts in users' browsers, leading to theft of sensitive information such as session cookies or credentials, unauthorized actions performed on behalf of users, and potential reputational damage. Although the vulnerability does not affect system availability, the compromise of confidentiality and integrity can have serious consequences, especially for organizations handling sensitive or regulated data. The requirement for user interaction limits the attack scope but does not eliminate risk, particularly in environments where users might be tricked into clicking malicious links or submitting crafted inputs. The absence of known exploits reduces immediate risk but should not lead to complacency. Organizations involved in domain registration services, web hosting, or IT service providers using this tool or similar codebases are particularly at risk. Additionally, sectors with high regulatory scrutiny such as finance, healthcare, and government entities in Europe must consider the implications of potential data leakage or session hijacking.

To mitigate this vulnerability, organizations should immediately review and update the affected code to avoid using innerHTML for rendering user-supplied data. Instead, use safe DOM manipulation methods such as textContent or createElement combined with proper encoding to neutralize malicious input. Implement comprehensive input validation and output encoding on all user inputs that are reflected in the UI. Applying a strict Content Security Policy (CSP) can help reduce the impact by restricting the execution of unauthorized scripts. Regularly audit web applications for DOM-based XSS vulnerabilities using automated scanning tools and manual code reviews. Educate developers on secure coding practices, especially regarding client-side scripting and DOM manipulation. If updating the Sourcecodester Domain Availability Checker is not immediately possible, consider isolating or disabling the vulnerable functionality until a patch is available. Monitor security advisories for updates or patches from the vendor or community. Finally, implement user awareness training to reduce the risk of social engineering attacks that might trigger this vulnerability.