I’ve just had the exact same problem and it was the seals which i’ve now replaced and no leaks whatsoever. All you need is as said above a seal kit from mojo, some PJ1 10w fork oil (or any other high quality motorcycle fork oil) and a 10mm socket to undo the bottom nuts on your fork.
If you’re just changing the seals you won’t even need to buy new fork oil but while youre there it might be worth doing it anyway.
1 – find out how much oil you’ll need in the damper side leg
2 – remove the fork from the bike and secure it upside down
3 – unscrew the bottom buts
4 – remove the lowers
5 – tip the fork the right way around over a pan to collect the oil. pump the damper to release the oil stored in it.
6 – use an open ended spanner to lever out the old seals
7 – fit the new seals
8 – pour new oil into damper side leg
9 – slide lowers back on over stanchions taking care not to mess up your new seals
10- screw the 10mm bottom nuts back on
That’s a rough guide but basically all you need to do. MOJO website (mojomedia>seal maintenance) gives a detailed step by step video. They’re not changing the oil so they leave the fork on the bike and just turn the bike upside down, but if you want to change the oil you’ll need to turn the fork upside down to tip it out.
Good luck! :)