Security readout for executives and security teams
Plain-English summary
CVE-2021-39341 affects the OptinMonster WordPress plugin through version 2.6.4. Weak authorization checks on REST API endpoints could let an unauthenticated remote attacker expose sensitive plugin data or change settings, including changes that may inject malicious web scripts into the site.
Executive priority
Prioritize remediation for public WordPress sites using OptinMonster because the flaw is remotely reachable without login and can affect customer-facing pages. No confirmed active exploitation is provided, but the low attack complexity and sensitive data exposure justify prompt action.
Technical view
The issue is insufficient authorization validation in the plugin's logged_in_or_has_api_key function in OMAPI/RestApi.php. The CVSS 3.1 score is 8.2: network reachable, low complexity, no privileges, no user interaction, with high confidentiality and low integrity impact.
Likely exposure
Exposure is limited to WordPress sites running OptinMonster up to and including 2.6.4, especially public sites where the plugin's REST API endpoints are reachable. The bundle does not identify affected CPEs or hosted-service exposure beyond the WordPress plugin.
Exploitation context
The source bundle does not list CISA KEV status and does not provide evidence of active exploitation. The described attack does not require authentication, which raises urgency for internet-facing WordPress deployments using the affected plugin version.
Researcher notes
Evidence is strongest for authorization failure and impact class, but incomplete on fixed version, exploit prevalence, and precise endpoint behavior. Do not assume active exploitation or a specific patch level from this bundle alone; verify against vendor and WordPress plugin release guidance.
Mitigation direction
- Inventory WordPress sites for the OptinMonster plugin and exact installed version.
- Treat versions up to and including 2.6.4 as vulnerable.
- Check OptinMonster, WordPress plugin, and Wordfence guidance for fixed versions or vendor mitigations.
- Update, disable, or remove vulnerable plugin installations according to vendor-approved guidance.
- Review recent site changes for unexpected OptinMonster settings or injected scripts.
Validation and detection
- Confirm whether OptinMonster is installed on each WordPress site.
- Record plugin versions and flag any version up to 2.6.4.
- Review WordPress logs for suspicious unauthenticated REST API access patterns.
- Inspect OptinMonster settings for unauthorized changes.
- Check site pages for unexpected third-party scripts or altered campaign content.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-285: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCWE-319: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2021-39341 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- High
- CVSS
- 8.2 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N3.94.2Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
8.2HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://www.wordfence.com/blog/2021/10/1000000-sites-affected-by-optinmonster-vulnerabilities/CVE reference · x_refsource_MISC
- https://wordfence.com/vulnerability-advisories/#CVE-2021-39341CVE reference · x_refsource_MISC
- https://plugins.trac.wordpress.org/browser/optinmonster/trunk/OMAPI/RestApi.php?rev=2606519#L1460CVE reference · x_refsource_MISC
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Improper Authorization
Improper Authorization represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.
Cleartext Transmission of Sensitive Information
Cleartext Transmission of Sensitive Information represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.