CVE-2021-24245

Stop Spammers <= 2021.8 - Reflected Cross-Site Scripting

2021-04-08 00:00

Strategic Overview

Status: Patched in 2021.9
Affected Plugin: Stop Spammers Classic
Affected Version: < 2021.9
CVSS: 6.1Medium
Weakness type: CWE-79 · Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CVE: CVE-2021-24245

View all Stop Spammers Classic vulnerabilities

At a glance

CVE-2021-24245 is a medium-severity Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in the Stop Spammers Classic WordPress plugin, affecting versions < 2021.9. It carries a CVSS score of 6.1 (reachable over the network; low attack complexity). Exploitation requires no authentication. The issue is fixed in version 2021.9; sites on affected versions should update now. Disclosed April 2021, reported by Hosein_vita.

Vulnerability Overview

The Stop Spammers WordPress plugin before 2021.9 did not escape user input when blocking requests (such as matching a spam word), outputting it in an attribute after sanitising it to remove HTML tags, which is not sufficient and lead to a reflected Cross-Site Scripting issue.

Technical Analysis

The vector marks this flaw as remotely reachable over the network, with low attack complexity — no special timing or configuration is needed, and no privileges on the target site.

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

Reaching this weakness in Stop Spammers Classic < 2021.9 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 Stop Spammers Classic the fix is 2021.9: builds < 2021.9 are affected, anything from 2021.9 onward is not.

Remediation

Update to version 2021.9, or a newer patched version

How does WordSec protect against this?

The attempt arrives as an ordinary request to Stop Spammers Classic: WordSec's web application firewall inspects request payloads before WordPress loads them. None of that substitutes for the fix: Stop Spammers Classic 2021.9 closes this, and updating the plugin is the step that ends it.

Firewall
Alerts

External References

https://www.cve.org/CVERecord?id=CVE-2021-24245 https://www.wordfence.com/threat-intel/vulnerabilities/id/2598ae85-5e91-47e6-b3f5-0d977fe80dd5 https://nvd.nist.gov/vuln/detail/CVE-2021-24245

Related records

Same weakness class

Other vulnerabilities in Stop Spammers Classic

CVSS Vector

6.1

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

Base

Attack VectorNetwork
Attack ComplexityLow
Privileges RequiredNone
User InteractionRequired
ScopeChanged
ConfidentialityLow
IntegrityLow
AvailabilityNone

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