Patch Tuesday is the day Microsoft has deemed to give us their vulnerability fixes.
It has to be done some time and so it is done on a Tuesday (right after Monday) and still in beginning of week. So the computer departments can schedule reboots and patching as soon as they are able.
the second Tuesday of the month is patch Tuesday
BetaNews discusses 6 bulletins, of which 2 are critical
Some affect different systems.
Technet advance discussion
Microsoft Security Bulletin
This one could be the bad one:
Vulnerability in Windows Journal Could Allow Remote Code Execution (2975689)
This security update resolves a privately reported vulnerability in Microsoft Windows. The vulnerability could allow remote code execution if a user opens a specially crafted Journal file. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights.
Please plan and patch accordingly