Microsoft will patch a critical bug in its Windows server software and two other vulnerabilities in PowerPoint. The two updates will be released at 1 p.m. ET on May 10. Microsoft also announced it would debut a changed exploitability index on Tuesday. The index, which debuted in October 2008, is a rating system that forecasts the likelihood a vulnerability will be exploited in the coming month. Microsoft habitually takes an even-odd approach, with fewer updates in even-numbered months featuring fewer updates.”]