Affects:
Spring: 5.3.9 but the error also occurs in earlier Versions (i could also reproduce it with 5.2.6)

Problem:
If a CommonsMultipartResolver is used to Handle File Upload to a Spring RestController and the LogLevel of the Dispatcher Servlet is set to DEBUG a Request Containing a Multipart File leads to an empty FileMap on the MultipartHttpServletRequest. If eighter the LogLevel is not DEBUG or another Resolver is used the same Request contains a FileMap,.

Expected Behavior:
The expected behavior would be that he LogLevel and the choice of the MultipartResolver do not change the behavior and the Request should always contain a File on the MultipartHttpServletRequest.

Example Application:
I created an example Application to check the behavior here:
https://gitlab.com/katja_m_franz/springbug
It is a really small Application and i hope you can easily reproduce the described Problem. All Info on how to do that can be found on the projects readme.