> This reveals that it's not the case and LLMs are already routinely hijacked to serve other people than their user

Meta's claim is that these were for their own support chatbot (which is also the conclusion the Wired article goes with). Not to give Meta the benefit of the doubt, but that does seem believable given the instructions were only present as "HelpContentGalaxyParagraph" within a script and some appear targeted at or specifically name their support bot.

Another non-Meta chatbot could in theory parse them out of the script and follow them, but I don't think it's as straightforward as this (AI-generated) article's "What you saw"/"What an AI was sent" example makes it out to be.