If you are running the Windows 10 PC Insider Preview build 10122, you might want to check out Windows Update. There should be three security patches that are available to download now.
All three updates were previously released for older versions of Windows. One of them, MS15-045, fixed this issue:
"The vulnerabilities could allow remote code execution if a user opens a specially crafted Journal file".
Another bulletin, MS15-038, deals with this problem:
"These vulnerabilities could allow elevation of privilege if an attacker logs on to the system and runs a specially crafted application."
Finally, the third update fixes problems with Internet Explorer:
"Resolves vulnerabilities in Internet Explorer that could allow remote code execution if a user views a specially crafted webpage by using Internet Explorer.
In related news, Windows Insider head Gabriel Aul confirmed via Twitter that Windows 10 build 10122 won't be offered for Slow ring members, stating, "There is a blocking bug on 7/8.x upgrades that breaks Start." He also confirmed that the company is interally testing a new build of the OS:
"There is a 10130 build, should not be a surprise :-) It's in our internal rings now."
Naturally, Aul didn't state when or if Windows 10 build 10130 will be released to all Windows Insider members.