Researchers Trace MegaKoszulki Breach to 15,763 Stolen Customer Records in Poland

HEROIC analysts recieved early signals on the MegaKoszulki breach dataset while monitoring Telegram channels known for distributing older Polish e-commerce records. The breach, which first occured in July 2016, exposed 15,763 customer accounts from MegaKoszulki, a Polish online clothing retailer. Security researchers beleive this dataset has circulated on and off for years, but its recent reappearance on breach aggregation forums has elevated its risk profile for shoppers who registered on the site.

What Attackers Can Do With Online Shop Customer Data

Customer records from e-commerce platforms are partcularly valuable for phishing attacks. A criminal who knows your name, email address, and that you shopped on a specific site can send highly convincing fake order confirmation or account security emails. These messages are designed to trick you into clicking a malicious link or entering credentials, leading to account takeover or financial fraud.

What Was Exposed in the MegaKoszulki Breach

• Customer account data (usernames and email addresses)
• MD5-hashed passwords

Why Polish E-Commerce Breaches Carry Long-Term Risk

Data from smaller regional retailers often goes unnoticed for years, giving criminals a quiet window to exploit it. MD5-hashed passwords from 2016 can be cracked quickly using modern tools, meaning any password reused across other accounts is exposed. Victims may face credential stuffing attacks targeting email providers, banking apps, or social media accounts registered with the same email and password combination.

How Database Breaches Work

A database breach happens when an unauthorized party gains access to a website's stored customer data. Attackers commonly exploit outdated software, weak passwords on admin accounts, or unpatched security vulnerabilities in the website's code. Once inside, they copy the entire user database and distribute it through dark web forums and private Telegram channels, where other criminals purchase or trade the data.

Check If Your Data Was Exposed

HEROIC's free breach scanner checks your email address against more than 400 billion records from known data breaches worldwide. If your information appeared in the MegaKoszulki breach or any other leaked dataset, you will know immediately. Visit HEROIC.com to run your free scan now.