I did a little bit of research the ST does not use the same slave cylinder as the regular Fiesta. They have that part listed as basically fitting every Fiesta so that can't be right.
But based on the picture it does look like an ST one, because the regular Fiesta part looks a little bit different they have that part listed wrong or something. If you do choose to buy it bring in your original one and compare it and make sure they look the same.
I know you need it in a hurry but heck you can order the OEM Ford part for $38
https://www.tascaparts.com/oem-parts/ford-slave-cylinder-dg9z7a564b?c=Zz1jbHV0Y2gmcz1oeWRyYXVsaWMtc3lzdGVtJmw9NSZuPUFzc2VtYmxpZXMgUGFnZSZhPWZvcmQmbz1maWVzdGEmeT0yMDE3JnQ9c3QmZT0xLTZsLWw0LWdhcw==
First picture non ST, second picture ST
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