It will spread further, but to an unknown extent. Usually it takes a while, ie months or years. I would disassemble carefully with the correct tools and neutralize & clean the corrosion. Usually for brittle plastic, I'll use a tool like this to aid in removal: https://www.amazon.com/dp/B01MFC7DMJ/

Soak the whole laptop in vinegar to neutralize & clean off the corrosion. Then do another soak in distilled water to remove the remaining vinegar residue. Dry thoroughly before turning it on.

I am joking.

local vinegar application will work though and neutralize the acid
then you clean it up and it's good to go

Thank you for your replies, I appreciate the help. I went for the cleaning, but it ended up being a disaster. It turns out that repairs had been done to the laptop by the previous owner. There were a lot of poorly soldered jumper wires to and from a daughterboard, which I couldn't see until it was too late, so I broke one of the jumper connections despite being very careful disassembling. I didn't break any plastic though, which was a surprise. Maybe the most frustrating part was that there was almost no corrosion on the hidden part of the board, so in the end I could've cleaned everything off with a riskless partial disassembly.

I couldn't see where the jumper wire snapped off and I couldn't find the right spot either. I tried soldering it to four spots that looked like they may have had a soldered connection in the past, but it didn't fix it. The jumper seems to be essential, because I tried a boot without it first and it didn't work. I got the same results no matter where I soldered the jumper: power light comes on and stays on, the pc speaker outputs static noise, black screen and no signs of life no matter what you press on the keyboard (I know setup is on F2).

I am very frustrated since I killed a laptop tonight that would have had a couple of months or years left to live. I don't blame you guys for it, I'm just frustrated with myself for killing my only Pentium-1. It's such a shame, because the laptop had a built-in SoundBlaster Vibra 16S too. I guess I will put the laptop in my laptop graveyard, where it can keep one of my Olivetti's company. Maybe it will come in handy someday for spare parts.

R.I.P. Tulip Motion Line ml 5/90.