Uber has acknowledged that a flaw in its software caused it to leak personal data belonging to its drivers.
The company said that about 700 of its "partners" in the US had been affected by the mistake.
Exposed data included social security numbers, photos of driver licences, tax forms and other details, according to news site Motherboard, which first reported the issue.
The error was discovered by the drivers themselves.
"Whoah - went to upload new insurance docs and the documents page showed me thousands of people private info (social security numbers, home addresses, tax info). I screencapped it and sent to support," wrote one driver on the discussion site Reddit.
It is not clear if anyone unconnected to the company was able to access the information before the problem was addressed.
"We were notified about a bug impacting a fraction of our US drivers earlier this afternoon," Uber said in a statement.
"Within 30 minutes, our security team had fixed the issue.
"We'd like to thank the driver who drew it to our attention and apologise to those drivers whose information may have been affected.
"Their security is incredibly important to Uber, and we will follow up with them directly."
This is not the first time the US company has had to tackle a security issue involving its drivers.
It previously acknowledged that in 2014 a hacker had been able to access a database containing current and former Uber drivers.