CVE-2023-33962 is a medium-severity (CVSS 5.4) Cross-site Scripting (XSS) vulnerability in io.jstach:jstachio. 1 public exploit reference exists, so weaponization risk is real. O3 Security confirms whether CVE-2023-33962 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
JStachio XSS vulnerability: Unescaped single quotes
Real-World Exposure
io.jstach:jstachioReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.
Description
JStachio is a type-safe Java Mustache templating engine. Prior to version 1.0.1, JStachio fails to escape single quotes ' in HTML, allowing an attacker to inject malicious code. This vulnerability can be exploited by an attacker to execute arbitrary JavaScript code in the context of other users visiting pages that use this template engine. This can lead to various consequences, including session hijacking, defacement of web pages, theft of sensitive information, or even the propagation of malware.
Version 1.0.1 contains a patch for this issue. To mitigate this vulnerability, the template engine should properly escape special characters, including single quotes. Common practice is to escape ' as '. As a workaround, users can avoid this issue by using only double quotes " for HTML attributes.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | io.jstach:jstachio | all versions | 1.0.1 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for io.jstach:jstachio. 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 io.jstach:jstachio to 1.0.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-33962 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 CVE-2023-33962 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 CVE-2023-33962. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2023-33962 in your dependencies?
O3 detects CVE-2023-33962 across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.