Security readout for executives and security teams
Plain-English summary
Custom 404 Pro for WordPress versions through 3.10.0 has a stored cross-site scripting issue. An attacker could cause malicious script to be saved and later run in a visitor or administrator browser. This can affect confidentiality, integrity, and availability at a limited level.
Executive priority
Treat this as a high-priority WordPress plugin exposure check. It is not documented as actively exploited in the provided sources, but stored XSS can affect privileged users and customer trust if present on public sites.
Technical view
CVE-2023-51540 is CWE-79 stored XSS in Kunal Nagar Custom 404 Pro. The CVSS 3.1 vector is AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:L with score 7.1. Sources state affected versions are through 3.10.0, but do not provide the vulnerable parameter, patch version, or workaround details.
Likely exposure
Exposure is likely limited to WordPress sites running the Custom 404 Pro plugin at version 3.10.0 or earlier. Confirm plugin presence and exact version because the source bundle has sparse affected-version metadata beyond the description.
Exploitation context
No cited source or KEV listing supports active exploitation. The CVSS vector indicates network reachability, low attack complexity, no privileges required, and required user interaction. Stored XSS generally depends on later page rendering by another user.
Researcher notes
The public data identifies stored XSS and CVSS impact, but omits vulnerable fields, proof-of-concept detail, exploit status, and fixed-version information. Do not assume a patch exists without checking current vendor or Patchstack guidance.
Mitigation direction
- Inventory all WordPress sites for the Custom 404 Pro plugin.
- Prioritize sites running Custom 404 Pro version 3.10.0 or earlier.
- Check Patchstack and vendor guidance for a fixed release or official workaround.
- Update the plugin when an official fixed version is confirmed.
- Disable or remove the plugin if no maintained fixed version is available.
Validation and detection
- Confirm installed plugin versions across production and staging WordPress instances.
- Verify vulnerability scanners flag no CVE-2023-51540 finding after remediation.
- Review site content and plugin-managed 404 settings for unexpected script content.
- Confirm security monitoring has no unexplained script injection indicators.
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-79: User-session and phishing behavior lookup
Client-side and session-facing weaknesses should be reviewed alongside initial-access and user-execution behaviors. 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-2023-51540 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
- 7.1 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:L
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:R/S:C/C:L/I:L/A:L2.83.7Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
7.1HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:L
Source materials
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 Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.