Hi Chakuttha,
We have application controls available for controlling upload to some well known websites. For any website which is not having such predefined controls available, we will need to investigate to identify the pattern on how upload is attempted and put rules to block. If you are asking for a one-rule-for-all to control upload, unfortunately it is not available now.
You can control upload by using the "Content-Length" header in a POST request. Do note that the control is based on an assumption that a file upload will have at least 10KB or more. You can use the article https://support.symantec.com/en_US/article.TECH241925.html as reference. This article is created for Download control but will be having same effect on uploads when the "Request" header is used.
Also you can use the article https://support.symantec.com/en_US/article.TECH241162.html for controlling request body size.