CVE-2020-35951

Quiz and Survey Master <= 7.0.0 - Unauthenticated Arbitrary File Deletion

2020-08-03 00:00
Chloe Chamberland

Strategic Overview

Status
Patched in 7.0.1
Affected Plugin
Quiz and Survey Master (QSM) – Quiz Maker & Survey Maker
Affected Version
< 7.0.1
CVSS
8.2High
Weakness type
CWE-639 · Authorization Bypass Through User-Controlled Key
CVE
CVE-2020-35951
View all Quiz and Survey Master (QSM) – Quiz Maker & Survey Maker vulnerabilities

At a glance

CVE-2020-35951 is a high-severity Authorization Bypass Through User-Controlled Key vulnerability in the Quiz and Survey Master (QSM) WordPress plugin, affecting versions < 7.0.1. It carries a CVSS score of 8.2 (reachable over the network; low attack complexity; high availability impact). Exploitation requires no authentication. The issue is fixed in version 7.0.1; sites on affected versions should update now. Disclosed August 2020, reported by Chloe Chamberland.

Vulnerability Overview

An issue was discovered in the Quiz and Survey Master plugin before 7.0.1 for WordPress. It allows users to delete arbitrary files such as wp-config.php file, which could effectively take a site offline and allow an attacker to reinstall with a WordPress instance under their control. This occurred via qsm_remove_file_fd_question, which allowed unauthenticated deletions (even though it was only intended for a person to delete their own quiz-answer files).

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, and no interaction from a victim user. A successful exploit has high impact on availability.

CWE-639: Authorization Bypass Through User-Controlled Key

Reaching this weakness in Quiz and Survey Master (QSM) < 7.0.1 takes no account at all. Authorization bypass through a user-controlled key, often called insecure direct object reference, means the application looks up a record by an identifier from the request without checking that the caller owns it.

Changing a number in the request is enough to read or modify other users' records, which on commerce and membership sites means customer data. For Quiz and Survey Master (QSM) the fix is 7.0.1: builds < 7.0.1 are affected, anything from 7.0.1 onward is not.

Remediation

Update to version 7.0.1, or a newer patched version

How does WordSec protect against this?

This one needs no account at all, which puts it outside what login hardening can reach; WordSec's login security narrows the account-level paths around it, and the firewall is what inspects the request itself. None of that substitutes for the fix: Quiz and Survey Master (QSM) 7.0.1 closes this, and updating the plugin is the step that ends it.

  • Login Security
  • Alerts

External References

https://www.cve.org/CVERecord?id=CVE-2020-35951https://www.wordfence.com/threat-intel/vulnerabilities/id/18458883-6cca-46d1-8437-4e646f4eafdahttps://nvd.nist.gov/vuln/detail/CVE-2020-35951

Related records

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