CVE-2000-0085 in Hotmail
Summary
by MITRE
Hotmail does not properly filter JavaScript code from a user's mailbox, which allows a remote attacker to execute code via the LOWSRC or DYNRC parameters in the IMG tag.
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Analysis
by VulDB Data Team • 04/20/2026
The vulnerability described in CVE-2000-0085 represents a classic cross-site scripting flaw that existed within the Hotmail webmail service during the early 2000s. This issue stemmed from inadequate input validation and output encoding mechanisms within the email rendering engine, specifically when processing HTML content within email messages. The flaw was particularly dangerous because it allowed attackers to inject malicious javascript code through email attachments or inline content, creating a persistent threat vector that could compromise user sessions and execute arbitrary commands on behalf of the victim. The vulnerability specifically targeted the handling of image tags with LOWSRC or DYNRC parameters, which were legacy html attributes that could be exploited to load remote content and execute code within the context of the user's browser session. This type of vulnerability falls under the CWE-79 category of Cross-Site Scripting, where web applications fail to properly sanitize user input before rendering it in web pages, creating opportunities for attackers to inject malicious scripts. The attack vector leveraged the principle of trust that users placed in their email clients, where legitimate emails containing malicious code could be executed without user awareness, effectively bypassing traditional security boundaries that separate trusted email content from potentially harmful scripts.
The operational impact of this vulnerability was significant as it enabled remote code execution capabilities that could be exploited to perform various malicious activities. Attackers could craft specially formatted emails that would execute javascript code when viewed in the Hotmail interface, potentially stealing session cookies, redirecting users to malicious sites, or even installing malware on the victim's system. The LOWSRC and DYNRC parameters in IMG tags were particularly problematic because they allowed for dynamic content loading, which created opportunities for attackers to reference external resources that could contain malicious payloads. This vulnerability represented a serious threat to email security and user privacy, as it could be exploited to compromise user accounts and potentially spread to other connected systems. The attack could be executed without requiring any special privileges or complex exploitation techniques, making it particularly dangerous for widespread deployment. From an attacker perspective, this vulnerability provided a reliable method for achieving persistent access to user accounts through the exploitation of web application security flaws. The vulnerability also demonstrated the importance of proper content sanitization in web applications, as the failure to properly validate and encode user-supplied content created opportunities for attackers to inject malicious code that could execute in the context of the victim's browser session.
Mitigation strategies for this vulnerability required immediate implementation of proper input validation and output encoding mechanisms within the web application. Organizations needed to ensure that all user-supplied content was properly sanitized before being rendered in web pages, with particular attention to html attributes and tags that could be exploited for code execution. The fix involved implementing robust content filtering that would strip or encode dangerous html attributes such as LOWSRC and DYNRC, preventing their execution in the browser context. Security measures should have included the implementation of content security policies that restricted the execution of inline javascript and limited the sources from which dynamic content could be loaded. Additionally, the vulnerability highlighted the importance of regular security audits and penetration testing to identify and remediate similar flaws in web applications. The incident served as a critical reminder of the need for defense-in-depth approaches to web application security, where multiple layers of protection work together to prevent exploitation of security vulnerabilities. Organizations needed to establish proper security protocols for handling user-generated content, including the implementation of web application firewalls and regular security updates to address known vulnerabilities. This vulnerability also emphasized the necessity of user education and awareness programs to help users recognize potentially malicious email content and understand the importance of not clicking on suspicious links or attachments in email communications. The remediation efforts should have included comprehensive testing of the patched application to ensure that legitimate functionality was preserved while eliminating the security vulnerability that had been exploited by attackers.