using input string CHECK in textbox resulting in faulty generation of site

[realSnoopy]

i noticed some misbehavior when is use the string CHECK as input in a textbox

result:
the site itself is generated, but the string is not processed and dokuwiki shows a message like this (see picture)

EDIT: it doesnt matter wheter CHECK, check or any variants

Bureaucracy up2date
version dokuwiki and php see picture