Vision Direct says that the personal details and payment card numbers, expiry dates and CVV codes of thousands of customers have been stolen by criminal hackers.
The online eyewear retailer says the theft involves all customers ordering or updating their information on visionDirect.co.uk between3-8 November.
The data was compromised when entering data on the website via a bogus Google analytics script and not from the Vision Direct database.
The personal information exposed includes full name, billing address, email address, password, telephone number and payment card information, including card number, expiry date and CVV.
About 6600 customers had their financial details compromised, while a further 9700 had personal date, but not card information, stolen.
"This particular breach is known as Shoplift and was already known to our technology team, who installed a patch provided by our web platform provider to prevent this form of malware," a spokeswoman told the BBC. "Unfortunately, this current incident appears to be a derivative against which the patch proved ineffective. We are continuing to investigate the breach and have made numerous steps to ensure this does not happen again."
Impacted customers are advised to contact their banks and inform them of the breach.