Data breaches → Yahoo
Was your data in the Yahoo breach?
2012 · yahoo.com · ~453,427 accounts exposedCritical severity · 9/10
Yahoo (yahoo.com) suffered a data breach in 2012 that exposed around 453,427 accounts. If you had an account, some of your personal data may be circulating in leaked databases. The fastest way to know is to check your own email — free, in about 30 seconds, no password required.
What happened
In July 2012, Yahoo! had their online publishing service "Voices" compromised via a SQL injection attack. The breach resulted in the disclosure of nearly half a million usernames and passwords stored in plain text. The breach showed that of the compromised accounts, a staggering 59% of people who also had accounts in the Sony breach reused their passwords across both services.
Breach details sourced from Have I Been Pwned, the industry-standard breach database. Risk analysis by Nullivo.
What was exposed, and why it matters
Not all breaches carry the same risk — what matters is which fields leaked. Here is what the Yahoo breach exposed and what each item actually enables:
Attackers replay leaked passwords across other sites (“credential stuffing”). Because most people reuse passwords, one leak often unlocks email, shopping and banking accounts elsewhere.
Puts you on spam and phishing lists, and confirms to attackers that you hold an account with this service — which makes impersonation emails more believable.
What to do if you were affected
These steps are ordered for this specific breach — the most urgent action given what leaked comes first.
- Passwords: Change this password everywhere you have reused it, starting with your email account — whoever controls your email can reset everything else.
- Email addresses: Treat any message referencing this service with suspicion, and never act on links in unexpected emails.
- Check whether your own email appears in this breach — run a free scan to confirm before you spend time on the steps above.
How urgent is this now?
This breach is over 14 years old. Old credentials still cause harm — leaked passwords from a decade ago are still tried against new accounts every day.
Passwords are the reason breach age matters less than people expect. Leaked credentials are compiled into wordlists that get tried against new services for years afterwards, so a password exposed here is unsafe to use anywhere, ever again.
Remember: a breach can't be "un-leaked" — once a database is out, it exists in countless copies. The goal is to make the leaked data useless: change what can be changed, lock down what can't, and remove what has been republished.
Frequently asked questions
What data was exposed in the Yahoo breach?
The Yahoo breach exposed passwords, email addresses. Attackers replay leaked passwords across other sites (“credential stuffing”). Because most people reuse passwords, one leak often unlocks email, shopping and banking accounts elsewhere.
How many people were affected by the Yahoo breach?
Around 453,427 accounts were exposed, making it a mid-sized breach.
What should I do if I had a Yahoo account?
Change this password everywhere you have reused it, starting with your email account — whoever controls your email can reset everything else. You can check whether your own email appears in this breach with a free Nullivo scan — no password required.
Breaches that exposed similar data
If the Yahoo breach affected you, these breaches exposed comparable information — worth checking too, since leaked datasets are routinely combined.
- Was your data in the League of Legends breach? (2012, ~339,487 accounts)
- Was your data in the War Inc. breach? (2012, ~1,020,136 accounts)
- Was your data in the Lookbook breach? (2012, ~1,074,948 accounts)
- Was your data in the YouPorn breach? (2012, ~1,327,567 accounts)
- Was your data in the Mecho Download breach? (2013, ~437,928 accounts)
- Was your data in the WHMCS breach? (2012, ~134,047 accounts)