We faced this issue during upgrade to eZ Platform v3 from eZ Publish. And seems like the only ezcontent:// links are used in eZ Platform v3, which makes hard to reproduce it on the clean eZ Platform v3.0.3 installation.
Steps to reproduce
1. Create a new Article, and embed location in its RichText field. The simplest way is to use https://gitlab.com/contextualcode/ezplatform-alloyeditor-source and add the following HTML:
2. Save the new article and open its full view page.
Embed location will be rendered
The following exception is thrown: