The latest Windows update appears to automatically enable "Fast startup" on certain Windows 10 systems. "Fast startup" functions by writing certain RAM contents to disk prior to shutdown, and then reading that data back into RAM during startup (similar to hibernation, but not as comprehensive). This allows Windows to start up more quickly. It can also cause your encryption keys and/or passwords to be written to disk prior to shutdown, which is basically a security nightmare. This is a known security issue which has been discussed previously, both on Wilders and elsewhere. The only reason I mention it now is because this latest update appears to automatically enable the feature without informing the user, thus creating a potential security risk which many users may not be aware of. Steps to reproduce the problem (there are undoubtedly others, but here is what I have found so far): If "Fast startup" is enabled (in Control Panel / Power options / Choose what the power buttons do), and if you have enabled "Cache passwords and keyfiles in memory" in TrueCrypt, and if you shut down your PC while a TrueCrypt volume is mounted (whether intentionally or due to a power failure), then when you restart your PC, Windows will automatically remount your volume without requiring you to input a password. The password will also be re-cached into memory. (Note: According to some online searches I performed, similar behavior has been seen in VeraCrypt, Diskcryptor and PGP Desktop.) This has obvious and serious security implications: 1) Any volumes that were mounted during shutdown will be remounted during startup without any input from you. Thus, anyone who can start or access your PC has full access to them. 2) Windows apparently stores your encryption keys and/or passwords on disk in order to make this feature work. This means that your encryption keys and/or passwords can likely be recovered from disk via simple forensic techniques, even if you subsequently dismount the volume. (I will try to confirm exactly what is written to disk: the keys, the passwords, or both). Please keep in mind that your encryption keys and/or passwords should NEVER be written to disk, they are meant to exist only in RAM and only while the system is running. If your keys have ever been written to disk, even just one time, then they are vulnerable to discovery and you need to generate new keys. This is why users of on-the-fly encryption software should never use hibernation or any other features that write the contents of RAM to disk. Solution: Disable "fast startup" to prevent Windows from storing your encryption keys and/or passwords on disk To see if fast startup is enabled in Windows 10: Control Panel / Power Options / Choose what the power buttons do Look at your Shutdown settings to see if "Turn on fast startup" is enabled To disable fast startup: Control Panel / Power Options / Choose what the power buttons do / Change settings that are currently unavailable / uncheck "Turn on fast startup" / Save changes Note: There are certain workarounds that can allow you to leave fast startup enabled, but I'm not sure how safe they are, so I'm not going to post them until I understand the situation more fully. Also, all of the above is preliminary information and is merely a heads-up. When I get some time I will try to nail down more of the specifics.