It is a very easy fix:
Unscrew the aluminum plate from the box
Take photo of the wiring and old post insulator colors - noting polarity
Disconnect signal wires from back of binding posts
Remove old binding posts from plate
Install new binding posts on plate
Reconnect signal wires to new binding posts with correct polarity
Reinstall plate to cabinet.
The original posts look like brass Dayton BPP. Replace them with at least solid brass like Dayton BPP, or better yet pure copper like WBT 703/708. Avoid the very inexpensive pot metal zinc posts like Dayton BPA. Also, anything above basic copper post is not necessary for subwoofer, like rhodium/platinum, fufutech, etc.
Take a peak at the internal post connection type to see what kind of terminals are on the wires before ordering. The internal wires will likely have round eye terminals, or F2 size (1/4") slip on terminals. It's OK to replace the wire terminals with a different type if you want to use new binding posts with a different type of internal connector terminal.
Speaker binding posts have a standard panel thru-hole size so any new standard posts should fit the old holes. You could measure with calipers or drill bits to be sure.
Cabinet is MDF, so tighten the wood screws only just firm enough to hold, not super tight because they will strip. Likewise don't overtighten binding post nuts, it is only brass or copper, not strong steel threads.
Make sure the rubber gasket inside the plate is fluffy enough to seal, otherwise replace it with new gasket strip. I use
this stuff, it crushes very flat, retains shape forever and it doesn't react w/oxygen and melt.
