XML isn't great for exchange/interchange either due to security problems and inconsistencies in implementations. A big part of the problem is that xml has a lot of complexity, which leads to a bigger attack surface when parsing and processing untrusted data. And then xml entities are just inherently insecure, unless you disable some of their capabilities (like using remote files, and unlimited recursion).

That said, creating a format that can convey rich untrusted data is a hard problem.