GHSA-mqqg-xjhj-wfgw
MEDIUMStored XSS in Miniflux when opening a broken image due to unescaped ServerError in proxy handler
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Blast Radius
miniflux.app/v2Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
Impact
Since v2.0.25, Miniflux will automatically proxy images served over HTTP to prevent mixed content errors.
When an outbound request made by the Go HTTP client fails, the html.ServerError is returned unescaped without the expected Content Security Policy header added to valid responses.
By creating an RSS feed item with the inline description containing an <img> tag with a srcset attribute pointing to an invalid URL like http:a<script>alert(1)</script>, we can coerce the proxy handler into an error condition where the invalid URL is returned unescaped and in full.
This results in JavaScript execution on the Miniflux instance as soon as the user is convinced (e.g. by a message in the alt text) to open the broken image.
An attacker can execute arbitrary JavaScript in the context of a victim Miniflux user when they open a broken image in a crafted RSS feed. This can be used to perform actions on the Miniflux instance as that user and gain administrative access to the Miniflux instance if it is reachable and the victim is an administrator.
Patches
PR #1746 fixes the problem. Available in Miniflux >= 2.0.43.
Workarounds
- Disable image proxy (default value is
http-only).
References
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | miniflux.app/v2 | ≥ 2.0.25&&< 2.0.43 | 2.0.43 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for miniflux.app/v2. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update miniflux.app/v2 to 2.0.43 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-mqqg-xjhj-wfgw is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-mqqg-xjhj-wfgw is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-mqqg-xjhj-wfgw. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-mqqg-xjhj-wfgw in your dependencies?
O3 detects GHSA-mqqg-xjhj-wfgw across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.