By illegal contents, are you referring to how somone posted a code signature similar to that of a virus so that antivirus software attacks the blockchain.
It's therefore a good idea there's a 40byte limit or a bitcoin node attacking virus could be placed in the code (and that would be a very good strategy)...
I mean, the last April-May issues and news with reports of pornographic images and illegal trade-related messages embedded in the blockchain.
Whereas those are stored as chunks of 40bytes of data using a specialized app to puzzle the image/text together.
(
Such sophistication for a simple thing)
That must be an indirect attack by adversaries and I have only mentioned it as a possibility.
And... we're getting off-topic.