CVE-2000-0085 is a high-severity vulnerability affecting Microsoft's Hotmail service, disclosed in early 2000. The core issue arises from Hotmail's improper filtering of JavaScript code embedded within users' mailboxes. Specifically, the vulnerability allows a remote attacker to inject and execute arbitrary JavaScript code via the LOWSRC or DYNRC parameters within the IMG HTML tag. These parameters can be manipulated to bypass standard input sanitization, enabling script execution in the context of the victim's mailbox session. This cross-site scripting (XSS) flaw can lead to unauthorized actions such as session hijacking, credential theft, or the execution of malicious payloads on the client side. The vulnerability is exploitable remotely without requiring authentication or user interaction beyond viewing the malicious email content. The CVSS score of 7.5 (AV:N/AC:L/Au:N/C:P/I:P/A:P) reflects the ease of exploitation over the network, no authentication requirement, and significant impact on confidentiality, integrity, and availability. Despite its age, this vulnerability highlights early webmail security challenges related to input validation and script filtering. No patch was available at the time of disclosure, and no known exploits in the wild were reported, but the potential for abuse was significant given Hotmail's large user base and the widespread use of webmail services.

For European organizations, the impact of this vulnerability could have been substantial, especially for enterprises and government entities relying on Hotmail for communication. Exploitation could lead to unauthorized access to sensitive emails, leakage of confidential information, and potential compromise of user credentials. This would undermine organizational security, potentially enabling further attacks such as phishing, identity theft, or lateral movement within corporate networks. The availability impact, while less direct, could result from malicious scripts disrupting user sessions or causing service instability. Given the widespread adoption of Hotmail in Europe around 2000, including among business users, the vulnerability posed a risk to both individual users and organizations. Although modern mitigations and the evolution of email platforms have since reduced exposure, at the time, European organizations with limited alternative secure email solutions were particularly vulnerable to such client-side script injection attacks.

Since no official patch was available for this vulnerability, European organizations and users needed to rely on alternative mitigation strategies. These include: 1) Avoiding the use of Hotmail for sensitive communications until the vulnerability was addressed; 2) Employing client-side security measures such as disabling JavaScript execution in the browser or using browser extensions that block script execution from untrusted sources; 3) Implementing email gateway filtering to detect and quarantine emails containing suspicious IMG tags with LOWSRC or DYNRC parameters; 4) Educating users about the risks of opening emails from unknown or untrusted senders and recognizing suspicious content; 5) Encouraging the use of alternative, more secure email services with robust input sanitization and script filtering; 6) Monitoring network traffic for unusual activity that could indicate exploitation attempts; 7) Applying strict Content Security Policies (CSP) in webmail clients to restrict script execution origins, if possible. These measures, while not perfect, would reduce the attack surface and limit the potential impact of this vulnerability.