By default, the built-in Recent Posts widget in WordPress only allows you to
display up to 15 recent posts max, even if you specify a larger number. This
is hard-coded into the WordPress core so any modifications you make would have
to be redone upon every WordPress update.
No longer!
The Recent Posts Widget Unlimited functions exactly as the built-in WordPress
widget but without the 15-post restriction. You can now specify an unlimited
number of recent posts to display without resorting to modifying the WordPress
core.