My browser / operating system: Windows NT 10.0, Chrome 91.0.4472.106, No Flash version detected
everything was fine yesterday but when i opened scratch today and went to my shared projects all of my projects were gonee !
then i saw that all of them were deleted and unshared yesterday

Contact the Scratch Team, either through here or by emailing help@scratch.mit.edu . There is no other way for anyone on the forums to help you, other than providing tips on avoiding getting hacked here, here, and here, along with not using common passwords (note: I am not responsible for any content on Wikipedia, and inappropriate content may be on Wikipedia as per WP:NOTCENSORED).

Change your password as FAST as possible, and make it strong, don't use a password that you've used for anything else.

Make sure that your email ID hasn't been changed, here under the Current Email section.

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Chiroyce wrote:

Change your password as FAST as possible, and make it strong, don't use a password that you've used for anything else.

[ad]Use my free password generator and generate a password up to 20 characters long at https://scratch.mit.edu/projects/516886727/ !!!![/ad]

kccuber wrote:

Use my free password generator and generate a password up to 20 characters long at https://scratch.mit.edu/projects/516886727/ !!!!

That isn't truly random, it's Pseudorandom. And the OP needs to use a password that they can remember.