CVE-2021-20840Network attack vector

Script execution via mishandled URL query parameters

Published Nov 24, 2021 · Updated Aug 3, 2024

Cross-site scripting in Saasproject Booking Package before 1.5.11 allows remote attackers to execute script via crafted URL queries. The plugin mishandles some URL query parameters, allowing attacker-controlled values to reach a page without sufficient output neutralization. Exploitation requires a site visitor to open the crafted URL; the script then runs in that visitor's browser and can read or alter data available to that page.

CVSS severity6.1
Medium
EPSS probability1.24%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cross-site scripting in Saasproject Booking Package before 1.5.11 allows remote attackers to execute script via crafted URL queries. The plugin mishandles some URL query parameters, allowing attacker-controlled values to reach a page without sufficient output neutralization. Exploitation requires a site visitor to open the crafted URL; the script then runs in that visitor's browser and can read or alter data available to that page.

The record

CVE
CVE-2021-20840
Published
Nov 24, 2021
Updated
Aug 3, 2024
Vendor
Saasproject
Product
Booking Package
Classifications
CWE-79, T1204.001
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Nov 24, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=versions prior to 1.5.11

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Saasproject · Booking Packageversion=versions prior to 1.5.11

Published CVSS scores

4.3NIST NVDAV:N/AC:M/Au:N/C:N/I:P/A:N
6.1JPCERT/CC JVNCVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
6.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
4.3JPCERT/CC JVNAV:N/AC:M/Au:N/C:N/I:P/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1204.001User Execution: Malicious Link

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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