Forever 21 has warned customers who used a credit card at any of its stores between March and October 2017 that their credit card may have been compromised.

According to Forever 21, its payment card readers were not encrypting credit card information during that time and it believes there may have been unauthorized access to the credit cards during that time. It has not indicated how many customers’ cards were compromised.

Forever 21 is advising its customers to check their monthly credit card statements and to notify their bank if there are any fraudulent charges.