From a Social Security newsletter (emphasis added):
We are required to conduct continuing eligibility reviews for disabled beneficiaries every three years. This process requires that beneficiaries complete a Continuing Disability Review mailer to update information about their medical conditions and recent treatments.
We now offer an online option to complete this update and provide any supporting documents about your medical treatment or your work.
We designed this new form with convenience in mind—and to save you time. You can access the online form at www.ssa.gov/ssa455-online-form. (Use either Microsoft Edge or Google Chrome for the best online experience.) ...
Once you “Click to Sign,” you will receive an email from echosign.com asking you to confirm your digital signature. Check your junk folder if you don’t receive it within a few minutes. Your signature isn’t complete—and your form won’t be processed—until you complete the instructions in your email.
I think this is the first time I've seen Social Security accepting digital signatures. Attorneys have been complaining for some time that Social Security won't accept digital signatures on documents submitted by attorneys.