CVE-1999-1453 is a vulnerability found in Microsoft Internet Explorer version 4.0, where remote attackers, specifically malicious website operators, can exploit the Internet WebBrowser ActiveX object to read the contents of the user's clipboard. This vulnerability arises because the ActiveX control improperly exposes clipboard data to web pages, allowing unauthorized access without user consent. The clipboard may contain sensitive information such as passwords, personal data, or other confidential content copied by the user. The attack vector is remote network-based, requiring no authentication, but exploitation is hindered by a high attack complexity, meaning that an attacker must craft a specific malicious web page and lure the user to visit it. The vulnerability impacts confidentiality only, with no effect on integrity or availability. Given the age of the vulnerability (published in 1999) and the affected product version (Internet Explorer 4.0), this issue is largely obsolete in modern environments. No patches are available, and no known exploits have been reported in the wild. The CVSS score is low (2.6), reflecting the limited impact and exploitation difficulty.

For European organizations, the direct impact of this vulnerability today is minimal due to the obsolescence of Internet Explorer 4.0, which is no longer in use or supported. However, if legacy systems or specialized industrial or governmental environments still operate this outdated browser version, there is a risk that clipboard data could be exposed to malicious websites, potentially leaking sensitive information. This could lead to privacy breaches or unauthorized disclosure of confidential data. The vulnerability does not allow code execution or system compromise, so the overall risk to operational continuity is low. Nonetheless, organizations with strict data protection requirements under regulations such as GDPR should be aware of any legacy systems that might be vulnerable to such clipboard data leakage.

Given that no patches are available for this vulnerability and the affected product is obsolete, the primary mitigation is to discontinue the use of Internet Explorer 4.0 entirely. Organizations should upgrade to modern, supported browsers that implement strict security controls around clipboard access and ActiveX controls. For environments where legacy systems must be maintained, network-level controls such as web filtering and restricting access to untrusted websites can reduce exposure. Additionally, user education to avoid visiting untrusted or suspicious websites while using legacy browsers can help mitigate risk. Implementing endpoint security solutions that monitor and restrict clipboard access by unauthorized applications or scripts may also provide an additional layer of defense.