Storing XML data for multiple users

I have an app (WebGL build) on the local network that runs users through a testing scenario (takes about 60 minutes to complete, then ends). Multiple users are accessing the app at the same time (approximately 20). I need to capture data from each user as they run the app (testing scores). I would like to output the data from each user as XML file, however I am not sure the best way to go about it. For example, can/should I have each of the users update the same XML file on the local network? Is there a better solution? Unfortunately, I am limited to simple text type output; I can’t use a database because of organizational limitations.

Any advice would be greatly appreciated.

Thanks,

Alex