"beforeupload" event does not work in Content Explorer

[Yelich6]

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Environment:

• Elements version:
  13.0.0, 11.0.2

Desktop (please complete the following information):

• OS: [Windows 10, Max OS 11]
• Browser [Chrome, IE11]
• Version [93.0.4577.82]

Steps to reproduce the problem:

When users tried to retrieve "beforeupload" events in Content Explorer,
it does not work. For example, an user attach the files in the Content Explorer, nothing happens.
On the other hand, Content Uploader is able to listen the event. Is it possible to detect "beforeupload" events in Content Exproler?

sample code:

contentExplorer.addListener('beforeupload', function(file) {
  console.log(`I am about to upload`);
});

What is the expected behavior? (Screenshots can be helpful here)

What went wrong? (Screenshots, console logs, or HAR files can be helpful here)

Link to application or sample code:

If relevant, link to file (or attach file here)

Expected behavior
A clear and concise description of what you expected to happen.

Screenshots
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https://cloud.box.com/s/js2eqvo8jmj3rhupi90jzjsh29bjpu6t
Additional context
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