New content, and updates to existing content, on the Steam Workshop will be going through a moderation process as an apparent response to scam content that leads to the hijacking of accounts.
The Steam Workshop is where modders can upload their content for the enjoyment of Steam users everywhere. It’s where you’ll find things like user-generated maps and item skins, but also a whole bunch of ads for free weapon skins for Counter-Strike: Global Offensive that bait users into giving away their account details.
In a recent post on Steam Support, it seems that Valve has introduced a two-step verification system for content coming out of the Steam Workshop, in order to prevent scams that lead to account theft. Now, every time you upload new content, or updates for older content, you will have to verify your email address and certain Workshops (ones with a history of being targeted by scams) will have their new or updated content go into a moderation queue. You can edit and view the content while the process is going on, but nobody else will be able to see it until it’s approved.
Valve has promised that the approval process will take less than a day and usually less than an hour.
It doesn’t seem like this process will be required for every Workshop, although the Support post isn’t really clear about what happens with content from Workshops with no history of scam activity. I assume they just have to pass the email verification step?