Twitter Inc urged its more than 330 million users to change their passwords after a glitch caused some to be stored in readable text on its internal computer system rather than disguised by a process known as "hashing."The social network disclosed the issue in a blog post and series of Tweets on Thursday afternoon, saying it had resolved the problem and an internal investigation had found no indication passwords were stolen or misused by insiders. Still, it urged all users to consider changing their passwords."We fixed the bug and have no indication of a breach or misuse by anyone," Chief Executive Jack Dorsey said in a Tweet. "As a precaution, consider changing your password on all services where you’ve used this password."The blog did not say how many passwords were affected. A person familiar with the company's response said the number was "substantial" and that they were exposed for "several months."