Strange/incorrect behavior of a fake executable file

[Vladimir Likic]

Configuration Information [Automatically generated, do not change]:
Machine: x86_64
OS: linux-gnu
Compiler: gcc
Compilation CFLAGS:  -DPROGRAM='bash' -DCONF_HOSTTYPE='x86_64'
-DCONF_OSTYPE='linux-gnu' -DCONF_MACHTYPE='x86_64-pc-linux-gnu'
-DCONF_VENDOR='pc' -DLOCALEDIR='/usr/share/locale' -DPACKAGE='bash' -DSHELL
-DHAVE_CONFIG_H   -I.  -I../. -I.././include -I.././lib  -Wdate-time
-D_FORTIFY_SOURCE=2 -g -O2 -fdebug-prefix-map=/build/bash-7fckc0/bash-4.4=.
-fstack-protector-strong -Wformat -Werror=format-security -Wall -no-pie
-Wno-parentheses -Wno-format-security
uname output: Linux sparky 4.9.0-6-amd64 #1 SMP Debian 4.9.82-1+deb9u3
(2018-03-02) x86_64 GNU/Linux
Machine Type: x86_64-pc-linux-gnu

Bash Version: 4.4
Patch Level: 12
Release Status: release

Description:

A strange/unexpected behavior when one creates a file with a single line
that is identical to the name of the file, gives exec permissions and
attempts to run the file.

Repeat-By:

$ echo junk > junk
$ chmod +x junk
$./junk
--> this completely destroys my system

Fix:
    [Description of how to fix the problem.  If you don't know a
    fix for the problem, don't include this section.]