WinHTTrack.exe has incorrect version property (3.48.19.0) instead of
(3.48.21.0) 
As I search in files "httrack-noinst-3.48.21.zip\httrack\src_win\" the problem
is in 3 files: 
1) httrack\src_win\WinHTTrack\WinHTTrack.rc (line 755-796)
...
// Version
...

2) \httrack\src_win\InnoSetup\httrack.iss (line 4-5)
AppVerName=WinHTTrack Website Copier 3.48-19
AppVersion=3.48.19

3) \httrack\src_win\InnoSetup\httrack-x64.iss (line 4-5)
AppVerName=WinHTTrack Website Copier 3.48-19 (x64)
AppVersion=3.48.19