CVE-1999-1235 is a medium-severity vulnerability affecting Microsoft Internet Explorer version 5.0. The issue arises because Internet Explorer 5.0 records usernames and passwords used for FTP server authentication directly in the URL history, specifically within the index.dat file. This file stores browsing history and can be accessed locally by other users on the same machine. Consequently, local users with access to the file system can retrieve sensitive FTP credentials of other users by examining the index.dat file. Additionally, the vulnerability exposes credentials through the browser's status bar: when a user hovers the mouse over a link containing FTP credentials, the status bar may display the full URL including the username and password, allowing an attacker physically observing the screen (shoulder surfing) to capture these credentials. The vulnerability does not require network exploitation or remote access; it is primarily a local information disclosure issue. The CVSS score of 4.6 reflects a medium severity, with the attack vector being local (AV:L), low attack complexity (AC:L), no authentication required (Au:N), and partial impact on confidentiality, integrity, and availability (C:P/I:P/A:P). No patches are available for this vulnerability, and no known exploits have been reported in the wild. Given the age of the vulnerability (published in 1999) and the specific affected version (Internet Explorer 5.0), modern systems are unlikely to be affected, but legacy environments or systems still running this outdated browser remain at risk.

For European organizations, the impact of this vulnerability is primarily related to the potential exposure of FTP credentials on shared or multi-user systems running Internet Explorer 5.0. If legacy systems are still in use, especially in sectors with strict data protection requirements such as finance, healthcare, or government, unauthorized access to FTP credentials could lead to unauthorized data access or exfiltration. The vulnerability could facilitate lateral movement within an internal network if attackers gain access to these credentials, potentially compromising internal file servers or sensitive data repositories. However, since exploitation requires local access or physical observation, the risk is limited to environments where multiple users share workstations or where physical security is lax. The lack of remote exploitation capability reduces the threat surface, but insider threats or attackers with physical access could leverage this vulnerability to escalate privileges or gather intelligence. Organizations relying on FTP for file transfers should be cautious, as compromised credentials could undermine the confidentiality and integrity of transferred data.

Given that no patch is available for this vulnerability, mitigation must focus on compensating controls. Organizations should: 1) Upgrade or replace Internet Explorer 5.0 with modern, supported browsers that do not store credentials in URL history. 2) Avoid embedding usernames and passwords in FTP URLs; instead, use secure authentication methods or dedicated FTP clients that do not expose credentials in URLs. 3) Implement strict access controls on shared systems to prevent unauthorized local access to user profiles and browsing history files such as index.dat. 4) Educate users about the risks of shoulder surfing and encourage awareness of sensitive information displayed in the browser status bar. 5) Where legacy systems must be maintained, consider isolating them in secure network segments with limited physical access. 6) Transition from FTP to more secure file transfer protocols like SFTP or FTPS that support encrypted authentication and data transfer. 7) Regularly audit and monitor access to critical systems to detect unauthorized local access attempts.