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NVD / CVE Program· CNA jpcert

CVE-2021-20840: Cross-site scripting vulnerability in Booking Package - Appointment Booking Calendar System versions prior to 1.5.11 allows a remote attacke

Noroxi assessment

Priority: Monitor (action score 24/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 1.2% (FIRST EPSS); higher than 70.2% of all records.
  • Anyone who can reach it over the internet can trigger it. No account or password is required. A user must open a link or visit a page. No special conditions are required; it is repeatable.
  • According to the record, no fixed version is available yet.

Low priority for now. Update when a fix is released; follow the vendor's advisory.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

Cross-site scripting vulnerability in Booking Package - Appointment Booking Calendar System versions prior to 1.5.11 allows a remote attacker to inject an arbitrary script via unspecified vectors.

MediumCVSS 6.1 · v3.1—No exploit No fix recorded
Published
Nov 24, 2021
Updated
Jun 16, 2026
EPSS
1.2% · 70th percentile

Report tools

JSON

Action score

24

Monitor

Low priority for now.

CVSS
24 / 40 · 6.1 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 1.2%

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  • when exploit code appears or is weaponized
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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
saasprojectbooking package

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • saasproject booking packagebefore 1.5.11

Versions reported by the vendor

Affected version ranges reported by the assigning authority (jpcert). Independent of NVD's CPE analysis and usually ahead of it.

  • Saasproject Booking Package - Appointment Booking Calendar System

    • versions prior to 1.5.11affected

Same product

saasproject: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-40774WordPress Booking Package plugin <= 1.7.06 - Broken Access Control vulnerability
    30Monitor
  • CVE-2024-30516WordPress Booking Package plugin <= 1.6.27 - Price Manipulation vulnerability
    30Monitor
  • CVE-2022-0709Booking Package < 1.5.29 - Unauthenticated Sensitive Data Disclosure
    30Monitor

Published before and after this one in the same product

  • Later →CVE-2023-39918Sep 4, 2023 · WordPress Booking Package Plugin <= 1.6.01 is vulnerable to Cross Site Scripting (XSS)
    24Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

No fix version is recorded for this entry. Check the references for vendor advisories.

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • A user must open a link or visit a page.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
low · data can be read
Integrity
low · data or configuration can be modified
Availability
none

Impact can extend beyond the vulnerable component (scope changes).

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
Required
Scope
Changed
Confidentiality impact
Low
Integrity impact
Low
Availability impact
None

Weakness class (CWE)

CWE-79 · Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

nvd-primary

Root cause

User content is inserted into the page as HTML. The browser interprets the content as code rather than data.

The bug in code

The whole CWE-79 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

ts
commentEl.innerHTML = comment.body;

Fixed

ts
commentEl.textContent = comment.body;

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

Change log

No changes recorded on tracked fields yet. Score, KEV, exploit maturity and fix status changes appear here.

References

Show all references (2 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records