So because a website HTML/CSS is protected computer program: an ad blocker intervenes in the in-memory execution structures of it; it constitutes an unlawful reproduction and modification.

This was first reject; but a new ruling sent the case back.

There are many reasons, in addition to ad blocking, that users might want their browser or a browser extension to alter a webpage.

As per BGH’s ruling, Springer’s argument needs to be re-examined to determine if DOM, CSS, and bytecode count as a protected computer program.

Mozilla noted that the new proceedings could take up to a couple of years to reach a final conclusion. As the core issue is not settled, there is a future risk of extension developers to be held liable for financial losses.