Technically, any hidden block that was hacked into the project with JSON editing is not allowed by ToU section 4.4. I also do not know of any project that has “legitimately” obtained such a block (as in the project was created in a Scratch version where the block was in the palette and it was used in the project). Are there any examples?

It'd be impossible to track. Blocks acquired through JSON editing and any other way are indistinguishable. I imagine a few would've come from backpacking or uploading projects years ago and made their way into newer projects. I think I backpacked one from a hacked block project, no idea where that project sourced its blocks from.

If it’s a showcase project, you can almost definitely say it was hacked in. “Legitimately” obtaining one means you created a project with it in a previous version where the block palette had it.

hotcrystal wrote:

(#3)
If it’s a showcase project, you can almost definitely say it was hacked in. “Legitimately” obtaining one means you created a project with it in a previous version where the block palette had it.

I think that awesome-llama understands this - it's just impossible to know.

The only projects where hacked blocks are legitimately obtained are some projects from 2.0 or less, but we can’t identify them as the above posts said.

Are there any known such projects?

hotcrystal wrote:

Are there any known such projects?

Not that I know of.

NotK3ndricAltAgain wrote:

The only projects where hacked blocks are legitimately obtained are some projects from 2.0 or less, but we can’t identify them as the above posts said.

I think it's possible: 1.x, 2.0 and 3.0 use different file formats, and all of them store the Scratch editor's version in the metadata.
For 2.0 projects the server still returns a 2.0-format project.json.
Through the API it's also possible to see when was the project last edited.

However, I don't think it looks different when a block is backpacked from an old project or from a hacked one or when it's hacked in directly.

Experimental_Blocks#Experimental_Control_Blocks_in_2.0
According to the Scratch wiki, most of the functional hidden blocks could never be obtained without hacking.

This is strange, because these blocks still work, but there are blocks that no longer work but they were in the block palette in earlier Scratch versions