# CVE-2026-86783: PostX < 5.0.41 - Unauthenticated Custom Field Key Disclosure via REST API

> Unauthenticated attackers can disclose custom field keys of private or protected posts via an unprotected REST API route in the Post Grid Gutenberg Blocks plugin.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 23 Sep 2026
- **Updated:** 23 Sep 2026
- **Also known as:** GHSA-f7w9-vf85-gjj5

## What is CVE-2026-86783?

CVE-2026-86783 is a medium-severity vulnerability in Unknown Post Grid Gutenberg Blocks, published on 23 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

The Post Grid Gutenberg Blocks  WordPress plugin before 5.0.41 does not perform an authorization or post-visibility check on a REST API route that returns the custom field keys of a given post, allowing unauthenticated users to disclose the custom field key names of arbitrary posts, including private, draft, pending, scheduled and password-protected posts.

Weakness: CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor)

## Which versions are affected by CVE-2026-86783?


## How do I fix CVE-2026-86783?

No fix has been published for CVE-2026-86783 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-86783 being exploited?

There is no known exploitation of CVE-2026-86783 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-86783 and fix it if it is affected.

What it is: CVE-2026-86783 is a medium-severity vulnerability in Unknown Post Grid Gutenberg Blocks, published on 23 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-86783 in the wild and no public exploit code.

Affected product: Unknown Post Grid Gutenberg Blocks. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-86783/ (Markdown: https://insights.sbomify.com/CVE-2026-86783/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-86783
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-86783
- OSV: https://osv.dev/vulnerability/CVE-2026-86783

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-86783/
Summaries are generated and may contain mistakes; the official description above is the record.