Expected Behavior:

Data is saved, and retrieved as entered

Actual Behavior:

If the following data is entered into a text field:

[{"content":"This is a \"some\" content"}]

What will be saved, and retrieved out of the database when accessed is:

[{"content":"This is a "some" content"}]

Note that slashes have been over-zealously removed. The data should be retrieved as-is without modification.

Steps to reproduce (I have confirmed I can reproduce this issue on the trunk branch):

1. Register a standard text field, e.g. as per the example.

$cmb_demo->add_field( array(
	'name'       => esc_html__( 'Test Text', 'cmb2' ),
	'desc'       => esc_html__( 'field description (optional)', 'cmb2' ),
	'id'         => $prefix . 'text',
	'type'       => 'text',
) );

2. Enter the following into the field:

[{"content":"This is a \"some\" content"}]

3. Save the entity. Note that what gets stored, and retrieved is:

[{"content":"This is a "some" content"}]

instead of

[{"content":"This is a \"some\" content"}]

Note: While I've reported this as an issue with the "text" type, the original bug I observed was with a custom field, within a repeatable group, so any fix probably needs to be generic across all field types, not just text.