Klarna Cyber Incident: What Happened and Why It Matters

The recent Klarna cyber incident has sparked widespread concern among users, especially given the company’s role as one of Europe’s most widely used ‘buy now, pay later’ services. Although Klarna insists the issue affected only a small number of customers, the event highlights important questions around digital security and identity protection.

What happened during the Klarna cyber incident

In late 2025, Klarna confirmed a technical fault that exposed limited customer data through its login system. The issue stemmed from mobile numbers being recycled by network providers:

• Klarna’s systems did not recognise when a number had been reassigned to a new customer.
• As a result, individuals who inherited recycled numbers could briefly see basic details of the previous number owner’s Klarna account.
• Exposed information was limited to names, email addresses and physical addresses.
• Klarna emphasised that no bank details, card information or transaction history were accessible.

Early internal estimates suggested the issue could have affected a large number of logins, but Klarna later clarified that the true scale was significantly smaller. The flaw has now been corrected, and additional safeguards have been introduced to prevent recurrence.

Why the security issue occurred

The incident was caused by a verification gap linked to recycled mobile numbers. Klarna’s login logic did not validate whether a number still belonged to the same customer, allowing a newly assigned user to initiate access. Klarna has since strengthened its verification checks to ensure ownership is double-confirmed before authorising account access.

The impact on customers and Klarna

For Customers

• Affected users may have had their personal details visible to someone unknowingly accessing their old number.
• While no financial data was exposed, the breach represents a serious privacy concern.
• There is a small risk that exposed details could contribute to identity fraud if combined with information from other sources.

For Klarna

• The incident created reputational damage and raised questions about the robustness of its verification systems.
• Initial internal projections suggested the company could face significant legal or compensatory costs.
• Klarna’s swift response helped limit further damage, but the event may still affect customer trust.

How Klarna responded to the incident

Klarna’s response was prompt: the flawed login logic was corrected as soon as the issue was identified, additional verification steps such as one-time passwords (OTPs) sent via email were introduced, and the company committed to notifying anyone who may have been affected. The firm has reiterated that the incident was limited, rare, and not part of a wider security breach.

Steps customers should take to stay secure

Although Klarna has resolved the issue, customers can protect themselves with a few simple steps:

• Check your Klarna account for any unfamiliar changes.
• Ensure your email address and password are up to date and secure.
• Turn on all available two-factor authentication options.
• Contact Klarna if you recently changed your mobile number to ensure your account details are correct.

These steps will help reduce the risk of unauthorised access and strengthen your account security.

What the incident reveals about digital identity risks

The Klarna incident illustrates a broader issue that affects many digital services: mobile numbers are often used for identity verification, yet they can change hands, sometimes without users realising. This incident shows the risks of relying solely on phone-number verification. Services that depend heavily on such methods may remain vulnerable unless they adopt more robust, layered security approaches such as device recognition, email-based verification and additional authentication factors.

Conclusion

Although the Klarna cyber incident affected only a small number of customers, it serves as a reminder of the vulnerabilities that exist within modern digital systems. Klarna has acted quickly to secure its platform, but the event underscores the need for continuous improvement in identity verification and data protection. For customers, it’s a valuable prompt to keep accounts secure, especially when changing mobile numbers or relying on phone-based login methods.

How AJC Can Help

At AJC, we understand how critical robust identity verification and digital security are, especially for organisations handling sensitive data or offering services requiring login authentication. If you want to review or strengthen your system architecture, user verification flows or security protocols, we’re here to help. Our experts can advise on best practices for:

• Multi-factor authentication (MFA/2FA) including email and device-based verification
• Secure login workflows avoiding sole reliance on mobile numbers
• Risk assessments for identity-based vulnerabilities
• Data-protection compliance and user-data segregation
• Incident-response planning to detect and recover from potential breaches

If you have any concerns about incidents like this or need support reviewing your organisation’s security posture, get in touch.

Contact us on 020 7101 4861 or email us at info@ajollyconsulting.co.uk if you think we can help.

Sources:

https://www.forbes.com/sites/christerholloman/2025/11/21/klarna-confirms-potential-customer-data-leak-but-wont-reveal-extent/

Image accreditation: Microsoft Edge (October 2022). Last accessed on 11th December 2025. Available at: https://unsplash.com/photos/a-woman-using-a-laptop-1N49Cn7P0Fg