UK challenger bank Starling is advising customers to change their passwords in the wake of a bug at internet infrastructure firm Cloudflare which saw sensitive information from some firms leaked.
Cloudflare provides security protection against things such as DDoS attacks to more than four million websites by routing traffic through its network.
According to a blog, after a tip-off from Google the firm discovered a simple code bug which led to website passwords, cookies and authentication tokens posted online in plain text over a period of several months from September.
Several financial services firms, including Coinbase, Betterment, TransferWise, Prosper, are on a list of potential victims. One Cloudflare client, Starling, took to Twitter to tell customers that it is investigating.
However, the challenger bank tells Finextra it has been told it is "not one of the 150 companies at the centre of the investigation by Cloudflare". Nevertheless, it is advising customers to change passwords as a "precautionary measure".
TransferWise also says that it has done a "full investigation" and "we are confident that TransferWise customer data is safe".
The Cloudbleed bug meant that some visitors to affected sites saw unencrypted private data from previous visitors along the bottom of tens of thousands of pages a day.
Cloudflare has been working with search engines such as Google and Bing to remove cached data but says it has not seen any malicious use of the information.