Google has let fly two new disclosures of Windows vulnerabilities before Microsoft was able to patch them, marking the third and fourth times it's done so in the past 17 days.
The bugs were revealed Wednesday and Thursday on Google's Project Zero tracker.
The more serious of the two allows an attacker to impersonate an authorized user, and then decrypt or encrypt data on a Windows 7 or Windows 8.1 device.
Google reported that bug to Microsoft on October 17, 2014, and made some background information and a proof-of-concept exploit public on Thursday.
Project Zero is composed of several Google security engineers who investigate not only the company's own software, but that of other vendors as well. After reporting a flaw, Project Zero starts a 90-day clock, then automatically publicly posts details and sample attack code if the bug has not been patched.
The team's previous disclosures of Windows bugs -- one on December 29, 2014, the second on January 11, 2015 -- led Microsoft to blast Google for putting its Windows customers at risk because neither vulnerability had been patched by the deadlines.
Microsoft fixed those flaws on Tuesday.
In the bug tracker for the impersonation vulnerability, Google said it had queried Microsoft on Wednesday, asking when the flaw would be patched and reminding its rival that the 90 days were about to expire.
"Microsoft informed us that a fix was planned for the January patches but [had] to be pulled due to compatibility issues," the bug tracker stated. "Therefore the fix is now expected in the February patches."
The next Patch Tuesday is scheduled for February 10.
The other issue had been disclosed Wednesday and could let an unauthorized user retrieve information about a Windows 7 PC's power settings. Even Google wasn't sure it was a security problem, however.
"It isn't clear if this has a serious security impact or not, therefore it's being disclosed as is," that bug's listing read.
Both disclosures, like the earlier pair, resulted from work by Google security engineer James Forshaw.
Microsoft confirmed the revealed-on-Thursday vulnerability.
"We're working to address the first case, CryptProtectMemory bypass," said a Microsoft spokesman in an email late Thursday. "We are not planning on addressing the second case, which may allow access to information about power settings, in a security bulletin."
Microsoft told Project Zero that it may deal with the power settings problem with a later, non-security fix. "Microsoft [has] stated that this issue is not considered serious enough for a bulletin release as it only allows limited information disclosure about power settings. It will be under consideration for fixing in future versions of Windows," the tracker said. "We agree with this assessment."
The spokesman added that Microsoft has seen no evidence of in-the-wild attacks leveraging the impersonation vulnerability. "To successfully exploit this, a would-be attacker would need to use another vulnerability first," the spokesman added.