There is only one file type that uses the .XMDX extension:
SofTest Answer File
An XMDX file is an answer file used by ExamSoft, an online assessment-management program. It contains the final, completed version of an exam, including the exam taker's answers. XMDX files are created by ExamSoft SofTest, which is a test-taking application available for Windows and macOS.
ExamSoft is a digital assessment platform that schools, businesses, and other entities use to test students, employees, and those seeking certifications. To take an ExamSoft exam, exam takers must download and install ExamSoft SofTest and then open an exam (.XMZX) file.
When a user finishes taking a SofTest exam, SofTest saves the user's completed exam as an XMDX file. It also automatically uploads the XMDX file to ExamSoft's cloud servers.
XMDX files are not meant to be opened. If you need to manually upload your XMDX file to ExamSoft's servers (for example, because you were not connected to the Internet when you finished your exam), you can find the file in SofTest's Answers directory. Then, you can manually upload the file at examsoft.com/manup.
Updated: May 28, 2021