Some have experienced data loss of their entire documents folder and other items. Back up your items and do not apply the update until MS can fix this. If you downloaded the update but it did not install you can follow these steps to delay the installation for 35 days. You also want to check off Pause Updates.

https://pureinfotech.com/prevent-windows-10-installing-april-2018-update-1803/

Here are my sources:

https://www.forbes.com/sites/jasonevangelho/2018/10/05/avoid-windows-10-october-update-until-you-do-one-thing/#371745273e79

https://www.reddit.com/r/Windows10/comments/9levfu/microsoft_windows_10_october_2018_update_can/

@thatwingsy
Oh my computer is off right now, so it my try to install the update when I turn it on lol. Hope nothing happens
@thatwingsy
Might* even
@thatwingsy
Lol my heart skipped a beat for a moment but it turns out I went to the wrong documents folder
@SilencingTrees Backup all the things!
@thatwingsy
Yeah I'm doing that. I don't have much in the regular Documents folder, just the Downloads folder which is outside it. Either way, I'm disabling updates for now!
@thatwingsy
Basically set my connection to metered for now
@thatwingsy
Oh wait they've already been downloaded. Need to find another way
@thatwingsy
I've checked it already but it doesn't work on my version of Windows 10 I think. I don't see some of those options
@SilencingTrees Huh that's weird. It should be on all versions?
@thatwingsy
I think they mention later is only for the pro versions. Anyway I've just noticed these aren't pending Windows updates so it's fine
@thatwingsy Apparently the update only rolled over for people who checked for it manually, as microsoft hasn't pushed it yet
@SilencingTrees I wonder if that's a way for them to "put the breaks" on the update because of the issue
@thatwingsy Nah I don't think so. The update is only set to roll out next week. You can still do it beforehand, but have to do so manually
@thatwingsy Also, I did some searching and read that windows sometimes creates an automatic profile during updates and moves your stuff there or something, so it isn't lost, just in another profile, and you can get it back
@thatwingsy This isn't necessarily the case this time though. It's just something that used to happen
@thatwingsy do we know if the data loss is a common thing?
@Dispregio I don't know. But this has happened to consumer as well as enterprise customers. It's probably large enough.
@thatwingsy yyyikes. I'm on the newest update but luckily I have places to back stuff up so I should be ok
@Dispregio That's good!
@thatwingsy @Dispregio The fact it hadn't been found until now means it's likely due to specific combinations of software and hardware. As others said...right now it's hard to pinpoint and most people have gotten on fine with the update. It's derp :(
@ceralor @Dispregio ive read that the preview copy had the same issue but wasnt fixed at release. According to the subreddit thread
@thatwingsy oh well, too bad. Already download the update on my work computer on Friday and turned it off.
Will have to look at it on Monday