Sharepoint online management shell--get user cookie

Add-Type -Path "C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\16\ISAPI\Microsoft.SharePoint.Client.dll"

Add-Type -Path "C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\16\ISAPI\Microsoft.SharePoint.Client.Runtime.dll"

$webUrl = "siteurl"

$username = "ankur@company.com"

$password = Read-Host -Prompt "Password for " -AsSecureString

$cred = New-Object -TypeName System.Management.Automation.PSCredential -argumentlist $username , $password

$onlineCred = New-Object Microsoft.SharePoint.Client.SharePointOnlineCredentials($username , $password)

$c = $onlineCred.GetAuthenticationCookie($webUrl )

$c

In the end you will get the cookie string if you have proper access.