WHSmith appears to have leaked personal contact information of those using one of the store's contact forms to a number of people around the country.
In a statement to the Huffington Post, WHSmith said the leak happened due to a "bug" in the system. According to its records fewer that 40 people have been affected.
"It is a bug not a data breach. We believe that this has impacted fewer than 40 customers who left a message on the ‘Contact Us’ page where this bug was identified, that has resulted in some customers receiving e mails this morning that have been misdirected in error. I-subscribe have immediately taken down their ‘Contact Us’ online form which contains the identified bug, while this is resolved. I-subscribe are contacting the customers concerned to apologise for this administrative processing error. We can confirm that this issue has not impacted or compromised any customer passwords or payment details and we apologise to the customers concerned.
Jono Read says the problem lies with the stores' magazine subscription service.
It is not yet clear if the breach is due to a hack or an IT glitch.
However, several have taken to Twitter to report how they woke up today morning to several spam-like emails containing phone numbers and email addresses of strangers.
One customer says he has received an apology for the data breach and tweeted:
Just spoke to @WHSmith - they are aware of and sorry for data breach. I'm still receiving private details of strangers #whsmithfail.
— Keن Day (@KenDay) September 2, 2015