Email marketing and newsletter service Mailchimp said it was hacked and that customer accounts were accessed last week, the second hacking incident in the last six months.

In a blog post last updated on Tuesday January 17th this year, the company said it identified someone accessing one of their customer service team’s tools to hack 133 accounts.

“The unauthorized actor conducted a social engineering attack on Mailchimp employees and contractors, and obtained access to select Mailchimp accounts using employee credentials compromised in that attack,” the company said.

A Mailchimp account used by e-commerce giant WooCommerce was one of the targets in last week’s hack, TechCrunch reported.

However, no customer passwords or other sensitive data was compromised although names, store addresses, and email addresses of its customers may have been exposed.

The company said that it has suspended access to the compromised accounts and informed account owners of the breach the day after the hack.

Mailchimp was affected by a similar data attack last year in which hackers breached approximately 300 accounts and exported audience data from 102 of those.

The marketing service best known for its email newsletter program had 2.4 million monthly active users and 800,000 paid customers as of October 2022, according to Bloomberg Intelligence.

“We know that incidents like this can cause uncertainty, and we’re deeply sorry for any frustration. We are continuing our investigation and will be providing impacted account holders with timely and accurate information throughout the process,” the post said.