When you replace the shoes on drum brakes, the new shoes force the brake cylinder piston seals to move further into the cylinder. If there is any corrosion or pitting in the wheel cylinder, the seals will be resting on the bad spot and will leak.
If you are feeling lucky check under the dust boots after a few miles and see if there is more leaked fluid. You may be lucky and the seals may still be sealing. You don’t want to let fluid leak out onto the shoes and drums as the shoes will have to be replaced again.
Follow Testers recommendation and replace the cylinder(s)