Summary
Stored XSS in October
Workarounds
Apply https://github.com/octobercms/october/commit/9ecfb4867baae14a0d3f99f5b5c1e8a979ae8746 & https://github.com/rainlab/blog-plugin/commit/6ae19a6e16ef3ba730692bc899851342c858bb94 to your installation manually if unable to upgrade to Build 466 or v1.4.1 of RainLab.Blog (if using that plugin).
References
Reported by Sivanesh Ashok
For more information
If you have any questions or comments about this advisory:
- Email us at [email protected]
Threat assessment:
Impact
A user with access to a markdown FormWidget that stores data persistently could create a stored XSS attack against themselves and any other users with access to the generated HTML from the field.
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-2020-11083 has a CVSS score of 3.5 (Low). The vector is network-reachable, high 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 (1.0.466); 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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Issue has been patched in Build 466 (v1.0.466) & RainLab.Blog v1.4.1 by restricting the ability to store JS in markdown to only users that have been explicitly granted the backend.allow_unsafe_markdown permission.
Frequently Asked Questions
- What is CVE-2020-11083? CVE-2020-11083 is a low-severity cross-site scripting (XSS) vulnerability in october/backend (composer), affecting versions >= 1.0.319, < 1.0.466. It is fixed in 1.0.466. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
- How severe is CVE-2020-11083? CVE-2020-11083 has a CVSS score of 3.5 (Low). 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 october/backend are affected by CVE-2020-11083? october/backend (composer) versions >= 1.0.319, < 1.0.466 is affected.
- Is there a fix for CVE-2020-11083? Yes. CVE-2020-11083 is fixed in 1.0.466. Upgrade to this version or later.
- Is CVE-2020-11083 exploitable, and should I be worried? Whether CVE-2020-11083 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-2020-11083 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-2020-11083? Upgrade
october/backendto 1.0.466 or later.