You can embed external images in reports if your administrator considers it safe to do so. If you try to add an image from an unapproved source, an error like this prompts you to contact your administrator.
Your administrator maintains a list of safe domains. For example, if you want embed images from *.example.org, ask your administrator to add this domain to the safe list. See Register Safe Domains.
In addition to images, your administrator can authorize or restrict access to other web resources, such as frames, scripts, fonts, stylesheets, audio, video, connections.