The .exe files contained in the installer have the following SHA1 hashes (Unicode and ANSI version respectively):

752e1687d58de3bef927d9ad24c0ed3da3754e17 *release/windirstat.exe
26e14a532e1e050eb20755a0b7a5fea99dd80588 *urelease/windirstat.exe

Provided on: https://windirstat.info/download.html

Hashes of the installer can be found here