High-flying stock trading fintech Robinhood has warned users to change their passwords after revealing that it stored the sensitive data in plain text, rather than an encrypted format, in its internal systems.

Users were made aware of the security mishap in a company email: “On Monday night, we discovered that some user credentials were stored in a readable format within our internal systems."

The firm goes on to say that the issue has been resolved and that it has found no evidence that the information was accessed by anyone outside its "response team".

The security blunder comes just days after Robinhood raised a massive $323 million round of financing, and amid a growing call for improved security at tech firms following recent privacy breaches at Facebook and Equifax.

The company has refused to disclose how many customers were impacted by the issue, nor how it came to make such a rooky error.