What if the form-data boundary is contained in the attached file?

Let's take the following example of multipart/form-data taken from w3.com:

Content-Type: multipart/form-data; boundary=AaB03x

--AaB03x
Content-Disposition: form-data; name="submit-name"

Larry
--AaB03x
Content-Disposition: form-data; name="files"; filename="file1.txt"
Content-Type: text/plain

... contents of file1.txt ...
--AaB03x--

It's pretty straight forward, but let's say you are writing code that implements this and creates such a request from scratch. Let's assume file1.txt is created by a user, and we have no control over its contents.

What if the text file file1.txt contains the string --AaB03x? You likely generated the boundary AaB03x randomly, but let's assume a "million monkeys entering a million web forms" scenario.

Is there a standard way of dealing with this improbably but still possible situation?

Should the text/plain (or even, potentially something like image/jpeg or application/octet-stream) be "encoded" or some of the information within "escaped" in some sort of way?

Or should the developer always search the contents of the file for the boundary, and then repeatedly keep picking a new randomly generated boundary until the chosen string cannot be found within the file?