100k Combo Yahoo 4 Leak Puts 83,240 Yahoo Accounts at Risk

100k Combo Yahoo 4 Leak Puts 83,240 Yahoo Accounts at Risk

On January 5, 2023, HEROIC analysts identified a stealer log labeled "100k Combo Yahoo 4," uploaded by a user on a Telegram channel. Despite the "100k" in its name, the actual file contained 83,240 records, each pairing an email address with a plaintext password and the URL the login was used on, filtered around Yahoo related accounts.

Why This Is Dangerous

Because this combo list appears to be filtered specifically around Yahoo accounts, attackers can point automated login tools directly at Yahoo's sign-in page using all 83,240 credentials at once, rather than wasting attempts on unrelated services. With passwords stored in plaintext, no additional cracking is required before an attacker can start testing logins.

What Was Exposed

• Email addresses
• Plaintext passwords
• URLs tied to each login

Why This Matters

A Yahoo account compromise can quickly become a bigger problem than it first appears, since Yahoo Mail is often used as a recovery address for other accounts. If an attacker gains access to one of these 83,240 accounts, they can potentially reset passwords on linked banking, shopping, or social media accounts, turning a single credential leak into a much broader case of account takeover and financial fraud.

How Stealer Logs Work

This file was assembled from infostealer malware infections, with criminals filtering the stolen credentials by email domain to isolate Yahoo accounts specifically, a common practice used to create targeted combo lists that are more valuable to buyers interested in a particular platform. The resulting 83,240 record file was then labeled and distributed through Telegram as the fourth in a series of similar Yahoo focused releases.

Check If You Are Affected

If you use a Yahoo email account, checking your exposure to this leak is worth doing right away. HEROIC's free breach scanner searches more than 400 billion leaked records, including targeted stealer logs like this Yahoo combo list, to show you if your email address has been compromised. Run a free scan and update your password immediately if you find a match.