Summary
JStachio XSS vulnerability: Unescaped single quotes
Description:
JStachio fails to escape single quotes ' in HTML, allowing an attacker to inject malicious code.
Reproduction Steps:
Use the following template code:
<div attr='{{value}}'></div>
Set the value variable to ' onblur='alert(1).
public class Escaping {
public static void main(String[] args) {
Model model = new Model("' onblur='alert(1)");
String result = AttributeTemplate.of().execute(model);
System.out.println(result);
}
@JStache(template = "<div attr='{{value}}'></div>",
name="AttributeTemplate")
@JStacheConfig(contentType= Html.class)
public static class Model {
public final String value;
public Model(String value) {
this.value = value;
}
public String getValue() {
return value;
}
}
}
Expected Result:
The resulting output should have properly escaped the single quotes and not execute the injected JavaScript code.
Actual Result:
The resulting output is vulnerable and renders as follows:
<div attr='' onblur='alert(1)'></div>
Impact and Risk:
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.
Proposed Solution:
To mitigate this vulnerability, the template engine should properly escape special characters, including single quotes. Common practice is to escape ' as '.
Workarounds
As long as users stick with double quotes " for HTML attributes, they should not be affected.
References
For instance, Rocker's general purpose HTML escaping
Impact
Untrusted input is rendered as active markup in a victim's browser, which can run script in their session. Typical impact: session or credential theft, and actions taken as the user.
CVE-2023-33962 has a CVSS score of 5.4 (Medium). The vector is network-reachable, low privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.0.1); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Frequently Asked Questions
- What is CVE-2023-33962? CVE-2023-33962 is a medium-severity cross-site scripting (XSS) vulnerability in io.jstach:jstachio (maven), affecting versions < 1.0.1. It is fixed in 1.0.1. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
- How severe is CVE-2023-33962? CVE-2023-33962 has a CVSS score of 5.4 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of io.jstach:jstachio are affected by CVE-2023-33962? io.jstach:jstachio (maven) versions < 1.0.1 is affected.
- Is there a fix for CVE-2023-33962? Yes. CVE-2023-33962 is fixed in 1.0.1. Upgrade to this version or later.
- Is CVE-2023-33962 exploitable, and should I be worried? Whether CVE-2023-33962 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2023-33962 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2023-33962? Upgrade
io.jstach:jstachioto 1.0.1 or later.