TicketWeb issued a second warning late last night following the weekend security breach by spammers purporting to offer an Adobe Acrobat upgrade.

The online ticket seller, who acknowledged the breach of their email database on February 12, issued a statement advising customers not to click the link after they had received up to four emails with the subject 'Action Required: Update Your PDF Application'.

The email claimed that the recipient's version of Adobe Reader was out of date and offered a link where they could download the new version. However, the link in fact lead to a malicious site.

The Ticketmaster subsidiary assured customers that they had closed the vulnerability and that "none of your credit card information was vulnerable during this attack".

But late yesterday TicketWeb sent out a second email for customers who had clicked through the link, which asked customers to enter their personal information and payment card details to third party websites.

TicketWeb said: "If you entered your card details upon following this link, you should contact your card issuer immediately. Your card issuer will advise you of the best course of action to take in your particular circumstances which may include the cancellation and repayment of your card.

"If you are issued with a replacement card, fraudsters will not be able to undertake fraudulent 'card-not-present' (internet shopping, telephone or mail order) activity on your account."

TicketWeb added that they would be liaising with the Information Commissioner's Office in relation to the security breach.