CVE-2021-24693

Simple Download Monitor <= 3.9.4 - Contributor+ Stored Cross-Site Scripting via File Thumbnail

2021-10-05 00:00

Strategic Overview

Status: Patched in 3.9.5
Affected Plugin: Simple Download Monitor
Affected Version: <= 3.9.4
CVSS: 9.0Critical
Weakness type: CWE-79 · Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CVE: CVE-2021-24693

View all Simple Download Monitor vulnerabilities

At a glance

CVE-2021-24693 is a critical-severity Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in the Simple Download Monitor WordPress plugin, affecting versions <= 3.9.4. It carries a CVSS score of 9.0 (reachable over the network; low attack complexity; high confidentiality, integrity, availability impact). The issue is fixed in version 3.9.5; sites on affected versions should update now. Disclosed October 2021, reported by apple502j.

Vulnerability Overview

The Simple Download Monitor WordPress plugin before 3.9.5 does not escape the "File Thumbnail" post meta before outputting it in some pages, which could allow users with a role as low as Contributor to perform Stored Cross-Site Scripting attacks. Given the that XSS is triggered even when the Download is in a review state, contributor could make JavaScript code execute in a context of a reviewer such as admin and make them create a rogue admin account, or install a malicious plugin

Technical Analysis

The vector marks this flaw as remotely reachable over the network, with low attack complexity — no special timing or configuration is needed. A successful exploit has high impact on confidentiality, integrity, availability — full site compromise territory.

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

Reaching this weakness in Simple Download Monitor <= 3.9.4 takes a caller who can reach the endpoint. Cross-site scripting happens when input from a request is written into a page without being escaped for the context it lands in, so the browser parses attacker-supplied text as markup or script.

Injected script runs with the privileges of whoever views the affected page, which is how these flaws turn into administrator session theft, silent account creation or persistent backdoors in page content. For Simple Download Monitor the fix is 3.9.5: builds <= 3.9.4 are affected, anything from 3.9.5 onward is not.

Remediation

Update to version 3.9.5, or a newer patched version

How does WordSec protect against this?

The attempt arrives as an ordinary request to Simple Download Monitor: WordSec's web application firewall inspects request payloads before WordPress loads them. None of that substitutes for the fix: Simple Download Monitor 3.9.5 closes this, and updating the plugin is the step that ends it.

Firewall
Alerts

External References

https://www.cve.org/CVERecord?id=CVE-2021-24693 https://www.wordfence.com/threat-intel/vulnerabilities/id/12ea26be-93e4-43de-bb32-21cdc2f80569 https://nvd.nist.gov/vuln/detail/CVE-2021-24693

Related records

Same weakness class

Other vulnerabilities in Simple Download Monitor

CVSS Vector

9.0

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

Base

Attack VectorNetwork
Attack ComplexityLow
Privileges RequiredLow
User InteractionRequired
ScopeChanged
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh

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