The reported behavior is explained in the following documentation article Using the Built-in Clipboard Tools, e.g.
The Cut , Copy and Paste tools use the native browser’s client-side commands to trigger the corresponding clipboard operation. Some browsers restrict such clipboard manipulations due to security matters, and thus the tools to not apply any changes. In such cases, the RadEditor prompts the end-user to use the keyboard shortcut combination to cut, copy or paste content ( Figure 3 ). More details about this security restriction is available in the Midas editor module security preferences MDN article.
Because of this limitation, we have enabled the browser's context menu in the content area so that the users can execute the copy/paste commands from it.
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