One of Apple's competitors in the mobile payment space sent out an email Wednesday telling users it had been breached.
CurrentC, which is a mobile payment system backed by the Merchant Customer Exchange (MCX), sent out an email to its pilot users stating that an unauthorized third party had obtained email addresses of some of its users, the MCX confirmed to CNBC in an email statement.
"Yes. Within the last 36 hours, we learned that unauthorized third parties obtained the e-mail addresses of some of our CurrentC pilot program participants and individuals who had expressed interest in the app. Many of these email addresses are dummy accounts used for testing purposes only. The CurrentC app itself was not affected.
We have notified our merchant partners about this incident and directly communicated with each of the individuals whose email addresses were involved. We take the security of our users' information extremely seriously. MCX is continuing to investigate this situation and will provide updates as necessary," a spokesperson for MCX said in a statement.
While CurrentC has not yet fully launched commercially, it has been in the spotlight recently because some of the retailers who are aligned with MCX, including CVS and Rite Aid, have disabled the technology in their stores that enables Apple Pay, CurrentC's rival.
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The group of retailers that make up MCX are developing CurrentC because they hope to gain access to more customer data and cut down on the high fees they are required to pay credit card companies for customer transactions.
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CurrentC differs from Apple Pay in several key ways.
For starters, CurrentC currently does not allow users to buy things with their credit cards. It only allows users to upload their bank account information to make mobile purchases. Apple Pay, however, enables consumers the ability to make purchases using whatever credit or debit card they wish.
Unlike Apple Pay, CurrentC is also not NFC enabled, meaning people cannot just tap their phone at checkout and be on their way. CurrentC requires users to scan a barcode to make a payment.
Because CurrentC does not require NFC it is compatible with more smartphones, while Apple Pay only works with the iPhone 6 and iPhone 6 Plus.
CurrentC also tracks information about a user's purchase history for merchants. CurrentC users can select what information they want to share with retailers and can opt out of marketing communications, according to the MCX website.
In contrast, Apple Pay does not track any buying or spending habits.
—By CNBC's Cadie Thompson. Follow her on Twitter @CadieThompson.