On 2014–11–13, Facebook introduced a new tracking code(metadata in it’s files). It appears as an IPTC Special Instructions metadata field. They look like:
"Special Instructions: FBMD01000ac60300004a1d00002d4b000067580000c9650000d5fc000054350100953a0100d3420100e84b01005f8f0100
Special Instructions: FBMD23000969010000b1590000cb7700000a8600000c07010046820100b8c0010052590200e5c902006e440300
So it's probably automatically added to images on Instagram, which is part of Facebook.
https://medium.com/mindorks/reading-metadata-from-images-cbcdb0be6573
I think FBMD.
On 2014–11–13, Facebook introduced a new tracking code(metadata in it’s files). It appears as an IPTC Special Instructions metadata field. They look like:
"Special Instructions: FBMD01000ac60300004a1d00002d4b000067580000c9650000d5fc000054350100953a0100d3420100e84b01005f8f0100 Special Instructions: FBMD23000969010000b1590000cb7700000a8600000c07010046820100b8c0010052590200e5c902006e440300
So it's probably automatically added to images on Instagram, which is part of Facebook.