Microsoft has released a first (security) update KB3074665 for Windows 10 build 10240 to fix issues reported so far, this update or MS calls it as a update package is now available via Windows Update to insiders in fast and ring, you need to be using build 10240 to receive this.

READ: Windows 10 build 10240 removes Desktop Watermark, improves Microsoft Edge Performance

Here is what Windows Insider head Gabriel Aul said on Twitter in a series of tweets about the update

We’re releasing an update package on WU for PC build 10240 today. It will install automatically or you can check for updates to grab it.
It is a package of fixes based on reported issues in 10240.
It will be described as a security update, but that’s just because it’s cumulative and includes the last package’s security fix

KB3074665 update

Here is how you can install the update: Open Settings > Update & Security > click on Check for Updates,

ALSO SEE: KB3070677 Update released for Windows 10 build 10130 allows Windows Update to detect new preview builds

Once the update is installed, restart your computer.

UPDATE: This KB3074665 page is offering below information.

Cumulative Security Update for Windows 10: July 17, 2015

This update addresses vulnerability in Adobe Flash Player in Windows 10 Internet Explorer 11.

For more information on vulnerability fixed, check Microsoft security advisory 2755801 and Adobe Security bulletin APSB15-18 

This update additionally includes ‘non–security-related changes to enhance the functionality of Windows 10 through new features and improvements.’

Have you installed this update successfully on your computer?