The installation of Microsoft Exchange 2000 before Rev. A creates a user account with a known password, which could allow attackers to gain privileges, aka the "Exchange User Account" vulnerability.

References

• https://nvd.nist.gov/vuln/detail/CVE-2000-1139
• https://docs.microsoft.com/en-us/security-updates/securitybulletins/2000/ms00-088
• https://exchange.xforce.ibmcloud.com/vulnerabilities/5537
• http://www.securityfocus.com/bid/1958