Google has restored its "personalized" search suggestions after purging the tool of a critical vulnerability that allowed attackers to steal a user's web history.

Personalized search suggestions were disabled on March 1, and they didn't return until April 20. Ordinarily, Google adds these personalized keyword suggestions to its generic suggestion list if you've turned on Google Web History, a service that stores your searches and page visits. The personalized suggestions are based on data from Web History.

In late February, a trio of security researchers - one at the University of California, Irvine and two at the French National Institute for Research in Computer Science and Control (INRIA) - sent Google a preliminary version of a paper showing how they were able to infer large portions of a user's web history by hijacking the user's session ID (SID) cookie and nabbing the company's personalized suggestion data. Google quietly disabled the personalized suggestions a week later.