CVE-2026-91122 — Discourse is an open-source discussion platform.¶
Key facts
CVE-2026-91122 is a High (8.7) vulnerability: Discourse is an open-source discussion platform.. This entry ships a detection-only PoC and a Docker test lab.
| CVE | CVE-2026-91122 |
| Severity | High (8.7) |
| Detection / prevention | — |
| PoC | poc.py |
| Source | 2026/CVE-2026-91122/ |
Details¶
English | 한국어
Description¶
Discourse is an open-source discussion platform. Prior to 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0, the video placeholder component allowed crafted HTML to cause an attribute breakout and inject an attacker-controlled event handler. An authenticated user with default trust-level posting privileges could store the crafted placeholder in a post. When another user opened the post and clicked the video play overlay, the handler could execute arbitrary JavaScript in the viewer's session. Default Content Security Policy settings block inline event handlers, but instances with CSP disabled or relaxed could allow the script to read page content and make authenticated requests as the viewer. This issue is fixed in versions 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0.
Vulnerability Details¶
| Property | Value |
|---|---|
| CVE ID | CVE-2026-91122 |
| Type | XSS |
| CVSS Score | 8.7 |
Proof of Concept¶
Download¶
# Download PoC script
curl -O https://raw.githubusercontent.com/fankh/vulnerability-poc/main/2026/CVE-2026-91122/poc.py
Usage¶
# Run PoC against target
python3 poc.py --target <TARGET_URL>
# With authentication
python3 poc.py --target <TARGET_URL> --username <USER> --password <PASS>
⚠️ Warning: This PoC is for authorized security testing only. It uses detection-only techniques and does not exploit or damage target systems.
Test Lab¶
This repository includes a Docker-based test environment with both vulnerable and patched applications.
Quick Start¶
# Clone and navigate to CVE directory
cd CVE-2026-91122
# Start both applications
docker-compose up -d
# Run tests
./run-tests.sh # Linux/Mac
./run-tests.ps1 # Windows PowerShell
Application Endpoints¶
| Application | URL | Status |
|---|---|---|
| Vulnerable App | http://localhost:8080 | Shows vulnerability |
| Patched App | http://localhost:8081 | Demonstrates fix |
Directory Structure¶
├── README.md # English documentation
├── README_KO.md # Korean documentation
├── poc.py # PoC detection script
├── docker-compose.yml # Container orchestration
├── run-tests.sh # Linux/Mac test runner
├── run-tests.ps1 # Windows test runner
├── vulnerable-app/ # Vulnerable version
│ ├── app.py
│ ├── Dockerfile
│ └── requirements.txt
└── patched-app/ # Fixed version
├── app.py
├── Dockerfile
└── requirements.txt
References¶
- https://github.com/discourse/discourse/commit/05d92b8749f68d2626cbe65ec7adde7562a0283d
- https://github.com/discourse/discourse/commit/5674b3e6594825c28d2678e55057fd6802f11031
- https://github.com/discourse/discourse/commit/c3993e318e172389be5c98455177876f1dd87dda
- https://github.com/discourse/discourse/commit/d7126af3264b672d2201d84c18a37cb8627424a8
- https://github.com/discourse/discourse/pull/42882
- https://github.com/discourse/discourse/security/advisories/GHSA-8m44-f6g9-7cg7
Generated by PoC Generator on 2026-09-27T12:33:48.948434335
Frequently asked questions¶
What is CVE-2026-91122?¶
CVE-2026-91122 is a High (8.7) vulnerability: Discourse is an open-source discussion platform.. This entry ships a detection-only PoC and a Docker test lab.
How do I detect CVE-2026-91122?¶
Run the detection-only PoC included with this entry against your Docker test lab to confirm whether a target is affected; pair it with your own IDS logging.
How do I block or mitigate CVE-2026-91122?¶
Upgrade to a fixed version per the vendor advisory; the NVD record lists the affected versions. Use the included PoC to verify your remediation.
For authorized security testing and research only. See the full source and NVD record.