Twitter has advised its more than 300m users to change their passwords after a bug caused "unmasked" passwords to be stored internally.
It added there was "no indication" that the details had been misused but warned users to update their login information as a precaution.
The company said in a statement: "We recently found a bug that stored passwords unmasked in an internal log.
"We fixed the bug and have no indication of a breach or misuse by anyone.
"As a precaution, consider changing your password on all services where you've used this password".
Twitter practice is to store passwords encrypted, or "hashed," so they are masked to even people inside the company, Twitter chief technology officer Parag Agrawal explained in a blog post.
"Due to a bug, passwords were written to an internal log before completing the hashing process", he said.
"We found this error ourselves, removed the passwords, and are implementing plans to prevent this bug from happening again".
The company did not specify how many passwords were exposed or how long the glitch made data vulnerable to snooping.
The stumble comes as the sector faces intense scrutiny over the protection of personal data online, in the wake of the Cambridge Analytica scandal which saw information from tens of millions of Facebook users hijacked and misused.
Chief Executive Jack Dorsey said recent changes made to the service have helped "engagement", a measure of how often people turn to the social network and how long they stay.
The company has stepped up efforts to boost its user base and engagement, adding streaming video partnerships, doubling the character limit on tweets to 280 and making it easier to create "tweet storms" by stringing messaging together.