Yahoo reported on Thursday that some of its users' e-mail accounts may have been targeted in a security breach of a third-party database.
"Recently, we identified a coordinated effort to gain unauthorized access to Yahoo Mail accounts," the company said in a blog post on its Tumblr site. "Upon discovery, we took immediate action to protect our users, prompting them to reset passwords on impacted accounts."
The company told users who may have been affected to reset their passwords. It has also implemented a second sign-in verification to allow users to re-secure their accounts.
"Impacted users will be prompted (if not, already) to change their password and may receive an email notification or an SMS text if they have added a mobile number to their account," the blog post said.
The California-based tech giant did not say how long it has been aware of the issue or how many accounts may have been compromised.
The compromise is the latest cyber attack in a slew of security breaches that have generated buzz in recent months.
(Read more: Target could face $1.1 billion in fines: Analyst)
Target announced on Wednesday that it believes cyber criminals who breached its networks in December used credentials they stole from one of the retailer's vendors.
Earlier this month, the mobile photo-sharing service Snapchat apologized to its users after anonymous hackers posted online usernames and partial phone numbers of 4.6 million of the app's users.
Yahoo shares dropped 1 percent in after-hours trading following the announcement.
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—By CNBC's Karma Allen. Follow him on Twitter @iam_karma.