CVE-2021-42663: An HTML injection vulnerability exists in Sourcecodester Online Event Booking and Reservation System in PHP/My

This month

MEDIUM 4.3DOWNGRADE

CVE-2021-42663 is a medium-severity flaw (CVSS 4.3) affecting online event booking and reservation system. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

An HTML injection vulnerability exists in Sourcecodester Online Event Booking and Reservation System in PHP/MySQL via the msg parameter to /event-management/index.php. An attacker can leverage this vulnerability in order to change the visibility of the website. Once the target user clicks on a given link he will display the content of the HTML code of the attacker's choice.

Why this priority

EPSS top 10%: very likely to be exploited
Public exploit reference

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	4.3 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	3.9% (top 10%)
CISA exploited list	No
Weakness	CWE-79
Published	2021-11-05
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: online event booking and reservation system project

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2021-11-05 13:15 UTCPublished CVE record published
2026-06-17 04:09 UTCUpdated Record last modified

online event booking and reservation system project online event booking and reservation system DOWNGRADE

Affected: 2.3.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 2.3.0

1. Check installed version

apt-cache policy online-event-booking-and-reservation-system || rpm -q online-event-booking-and-reservation-system || online-event-booking-and-reservation-system --version

2. No fixed release: DOWNGRADE to a release before 2.3.0 (Debian / Ubuntu)

apt-cache madison online-event-booking-and-reservation-system sudo apt install online-event-booking-and-reservation-system=<VERSION_BEFORE_2.3.0> sudo apt-mark hold online-event-booking-and-reservation-system

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list online-event-booking-and-reservation-system sudo dnf downgrade online-event-booking-and-reservation-system-<VERSION_BEFORE_2.3.0> sudo dnf versionlock add online-event-booking-and-reservation-system

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

Nuclei scan template: Sourcecodester Online Event Booking and Reservation System 2.3.0 - Cross-Site Scripting

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-42663?

online event booking and reservation system: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-42663 being exploited?

CVE-2021-42663 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2021-42663 affect?

CVE-2021-42663 affects online event booking and reservation system. Severity is medium (CVSS 4.3). An HTML injection vulnerability exists in Sourcecodester Online Event Booking and Reservation System in PHP/MySQL via the msg parameter to /event-management/index.php. An attacker can leverage this vulnerability in order to change the visib

How urgent is CVE-2021-42663?

Priority 43/100. EPSS top 10%: very likely to be exploited; Public exploit reference

Software pages

PHP vulnerabilities · MySQL vulnerabilities

Related CVEs

CVE-2021-42667 CRITICAL 9.8 DOWNGRADE A SQL Injection vulnerability exists in Sourcecodester Online Event Booking and Reservation System in PHP in e
CVE-2021-42662 MEDIUM 5.4 DOWNGRADE A Stored Cross Site Scripting (XSS) vulnerability exists in Sourcecodester Online Event Booking and Reservatio

References

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