A hack of Gawker's commentor boards has trickled down to several sites across the Web, including LinkedIn, Yahoo, and Blizzard's "World of Warcraft." These and other companies have issued password resets to customers they believe might have been affected.

LinkedIn said Tuesday that it identified a "very small fraction" of its members whose accounts were potentially compromised by the Gawker attack, and sent them instructions for a password reset.

"As we closely monitored the situation, we decided it was imperative to take preemptive action to help ensure that those leaked passwords were not being used to attack any LinkedIn members," Vincente Silveira, principal product manager at LinkedIn, said in a blog post.

Yahoo and Blizzard took similar action.

"As part of our ongoing security measures we issued a password reset to some users. Yahoo does this periodically to ensure the security of users," a Yahoo spokeswoman said in a statement.

"To help minimize the effects of this compromise - namely for players who might be using the same login information for their Gawker Media accounts and their Battle.net accounts - we issued password-reset emails for several accounts," Blizzard said in a note on its Web site.

A Blizzard spokeswoman declined to reveal how many WoW players were affected.

At issue is a weekend hack that accessed Gawker's commentor database, which is home to about 1.5 million usernames, e-mails, and passwords. Gawker urged its users to change their passwords immediately, especially if they use that same password on other Web sites. The password vulnerability led to a Twitter spam attack on Monday.

The FBI confirmed Tuesday that it is investigating the Gawker hack, which was reportedly carried out by a group known as Gnosis.

Editor's Note: This story was updated at 2:45pm Eastern with comment from Blizzard.