CVE-2021-4387 | Opal Estate <= 1.6.11 - Cross-Site Request Forgery Bypass

Exp

The Opal Estate plugin for WordPress is vulnerable to Cross-Site Request Forgery in versions up to, and including, 1.6.11. This is due to missing or incorrect nonce validation on the opalestate_set_feature_property() and opalestate_remove_feature_property() functions. This makes it possible for unauthenticated attackers to set and remove featured properties via a forged request granted they can trick a site administrator into performing an action such as clicking on a link.

Published: 2023-07-01 Last update: 2026-06-17 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-4387 is rated Exploit Available (50/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.58%). 1 public exploit reference(s) are indexed (Exploit-DB). Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2021-4387

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2021-4387

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-07-02 0.50% 0.58% +0.08%
2 2026-06-15 0.17% 0.50% +0.33%
3 2026-04-27 — 0.17% —

Full EPSS history (19 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-4387

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
4.3 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N)
Service keeps running; no real outage angle.
 2.8 1.4 [email protected]
8.8 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 2.8 5.9 [email protected]

Weakness enumeration for CVE-2021-4387

Affected software / configurations for CVE-2021-4387

Vendor Product Version Raw CPE
wpopal opal_estate <= 1.6.11 cpe:2.3:a:wpopal:opal_estate:*:*:*:*:*:wordpress:*:*

References for CVE-2021-4387

URL Tags
https://blog.nintechnet.com/25-wordpress-plugins-vulnerable-to-csrf-attacks/ Third Party Advisory
https://blog.nintechnet.com/more-wordpress-plugins-and-themes-vulnerable-to-csrf-attacks/ Third Party Advisory
https://blog.nintechnet.com/multiple-wordpress-plugins-fixed-csrf-vulnerabilities-part-1/ Third Party Advisory
https://blog.nintechnet.com/multiple-wordpress-plugins-fixed-csrf-vulnerabilities-part-2/ Third Party Advisory
https://blog.nintechnet.com/multiple-wordpress-plugins-fixed-csrf-vulnerabilities-part-3/ Third Party Advisory
https://blog.nintechnet.com/multiple-wordpress-plugins-fixed-csrf-vulnerabilities-part-4/ Third Party Advisory
https://blog.nintechnet.com/multiple-wordpress-plugins-fixed-csrf-vulnerabilities-part-5/ Exploit Third Party Advisory
https://plugins.trac.wordpress.org/browser/opal-estate/trunk/inc/ajax-functions.php#L177 Not Applicable
https://www.wordfence.com/threat-intel/vulnerabilities/id/2645899c-2b6b-48bd-8f33-2a837a951c5e?source=cve Third Party Advisory
cvelogic Threat Intelligence