Curious mark on wood veneer

[supersprouts]

A few days ago I noticed a curious long mark on the veneer of a wall-mounted loudspeaker. It seems to be made from veneered chipboard. There also appears to be some disturbance of the chipboard edge at the back of the speaker. I'm wondering if there's a worm or beetle working it's way along the wood. I don't really want to take the speaker apart but I've just noticed that the joint at the bottom is splitting away. Have you any idea what this may be?

I’ve never seen anything like that before !!! If it were running down wards I’d guess at liquid damage but it’s going horizontal ? Were there any bits of wood/ sawdust on the floor under it ?

Yes, you're right - it's running horizontal. I can't see any woody dust below it. There's a bit of a disturbance of the chipboard edge at the back as shown on the photo, but nothing else. If it's something that's laying eggs in there which will hatch out and cause more damage I'd rather destroy it - but at the moment it's a reasonable loudspeaker!