Three hackers said they had exploited a vulnerability in Research In Motion’s PlayBook tablet to gain root access to the device, a claim that could damage the BlackBerry maker’s hard-won reputation for security. The hackers plan to release their data within a week as a tool called DingleBerry. In a response to queries, RIM said it is investigating the claim, and if a jailbreak is confirmed will release a patch to plug the hole. The PlayBook runs on a different operating system than RIM’s current BlackBerry smartphones. However, the QNX system will be incorporated into its smartphones starting next year. The PlayBook in July became the first tablet device to win a security certification approving it for U.S. government use.