The bug originally observed in a forum thread https://www.zabbix.com/forum/showthread.php?p=125033#post125033
And I can confirm it:
- zabbix_get -s localhost -k vfs.file.contents[/tmp/ttt]
?u??$
- ls -la /tmp/ttt
rw-rr- 1 root root 0 Jan 21 14:41 /tmp/ttt
The issue reproduced for agent under windows as well.
Some more details will be added as a comment.