Yahoo! Inc. said today that a security breach on its siteexposed 450,000 user names and passwords for accounts at Yahoo andother Internet services such as Microsoft Corp.'s Hotmail and AOLInc.

A file containing login credentials for Yahoo and other accountswas stolen from a Yahoo site featuring user articles, videos andslideshows on July 11, the company said in an e- mailed statementtoday.

“At Yahoo we take security very seriously and invest heavily inprotective measures to ensure the security of our users and theirdata across all our products,” the Sunnyvale, California-basedcompany said in the statement. ''We are taking immediate action byfixing the vulnerability that led to the disclosure of this data,changing the passwords of the affected Yahoo! users and notifyingthe companies whose users accounts may have been compromised. Weapologize to all affected users.''