WYSIWYG editor accepts HTML with embedded images but doesn't display them correctly

[Daniel Lenski]

If I paste HTML containing images embedded via data: URIs into the WYSIWYG editor in Confluence 5.9.3, then…

• In the WYSIWYG editor, the embedded images are displayed correctly
• When viewing the resulting pages, the embedded images are not shown, and replaced with a red box saying "Broken Image"

This is really frustrating, because it means that there's no way to paste rich text containing images directly into the Confluence WYSIWYG editor, while ensuring that the images on the resulting page will be viewable by page viewers.

Here is an example of HTML that will trigger this misbehavior:

<h1>Here is a small picture of a cute monkey</h1>

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