The hack redirected readers to the page of the Syrian Electronic Army, a group that backs Syrian President Bashar Assad, the Post said in an online posting.
"We've taken defensive measures, and at this time there are no other issues affecting the site," Emilio Garcia-Ruiz, the Post's managing editor-digital, said.
In a tweet Thursday morning, the Syrian Electronic Army claimed credit for the attack, indicating the Post's site was hacked through Outbrain, an ad network used by the newspaper.
The hacking came after a "phishing" attack by an unidentified source this week gained access to a staff writer's computer account, Garcia-Ruiz said.
Officials at the Post said they believed the Syrian Electronic Army was also the source of the phishing scam.
The hack lasted for about 30 minutes and affected a number of foreign-news stories, the Post said.
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