Steps to reproduce:

• Create new page in Internet Explorer 11
• Paste an image into the editor
• Watch the upload dialog saving the image as attachment
• Press Cmd+Z (MacOS) / Ctrl+Z (Windows or Linux)

Expected result:

• Image is removed

Actually happens:

• Image is still visible, sometimes it gets resized (larger)
• There's a highlighted square in the top left corner of the image and another Cmd+Z/Ctrl+Z is needed to remove it

Notes:

• If saved, the image is not stored on the page
• This may be related to similar bug in other browsers but with different symptom: CONFSERVER-59623
• Collaborative editing does not seem to have any effect on this bug