Skip to content

ApostropheCMS sanitize-html: nonTextTags discard region ends early on an implied close, letting <noscript> content render

Moderate severity GitHub Reviewed Published Oct 2, 2026 in apostrophecms/apostrophe • Updated Oct 20, 2026

Package

npm sanitize-html (npm)

Affected versions

< 2.18.0

Patched versions

2.18.0

Description

Summary

sanitize-html discards the content of every element in nonTextTags. It delimits that region
using htmlparser2's close events, and ignores the isImplied flag htmlparser2 passes it. Closing a
still-open ancestor from inside a <noscript> makes htmlparser2 unwind its stack past the
noscript; the synthetic implied close it emits on the way ends the discard region early, and
everything after it is treated as ordinary body content.

A browser with scripting enabled parses <noscript> content as raw text, so the same markup
renders as inert text there. The sanitizer therefore emits elements the page itself would not have.

Reproduction

const sanitizeHtml = require("sanitize-html");

sanitizeHtml('<div><noscript></div><img src="http://evil.test/t.gif"></noscript>', {
  allowedTags: ["div", "img"],
  allowedAttributes: { img: ["src"] },
  nonTextTags: ["script", "style", "textarea", "option", "noscript"],
});
// => '<div></div><img src="http://evil.test/t.gif" />'

Chrome, given the same input, renders no <img> — the whole payload is raw text inside the
unclosed <noscript>. Verified with Playwright, srcdoc into an iframe so the scripting flag is on.

A <![CDATA[ variant hides the opening tag from the parser entirely and has the same effect:

<p>Hi</p><![CDATA[ x > <noscript>]]><a href="…">Reset your password</a><img src="…beacon.gif"></noscript>

htmlparser2 runs a CDATA token to ]]>; Chrome ends a bogus comment at the first >, so the
<noscript> after it is real to the browser and invisible to the parser.

Where the behaviour is

index.js:

  • :154 — nonTextTagsArray (the default list, ['script','style','textarea','option','xmp']).
  • :638 — onclosetag: function (name, isImplied) — receives the flag.
  • :644 — skipTextDepth-- — decrements without consulting isImplied.

Suggested fix

Do not end a discard region on an implied close. htmlparser2 already distinguishes them; the flag
is passed and discarded. Something close to:

onclosetag: function (name, isImplied) {
  if (skipText) {
    if (isImplied) return;   // an implied close must not end the region
    skipTextDepth--;
    …

References

@boutell boutell published to apostrophecms/apostrophe Oct 2, 2026
Published to the GitHub Advisory Database Oct 20, 2026
Reviewed Oct 20, 2026
Last updated Oct 20, 2026

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v4 base metrics

Exploitability Metrics
Attack Vector Network
Attack Complexity Low
Attack Requirements None
Privileges Required Low
User interaction None
Vulnerable System Impact Metrics
Confidentiality Low
Integrity Low
Availability Low
Subsequent System Impact Metrics
Confidentiality None
Integrity None
Availability None

CVSS v4 base metrics

Exploitability Metrics
Attack Vector: This metric reflects the context by which vulnerability exploitation is possible. This metric value (and consequently the resulting severity) will be larger the more remote (logically, and physically) an attacker can be in order to exploit the vulnerable system. The assumption is that the number of potential attackers for a vulnerability that could be exploited from across a network is larger than the number of potential attackers that could exploit a vulnerability requiring physical access to a device, and therefore warrants a greater severity.
Attack Complexity: This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. These are conditions whose primary purpose is to increase security and/or increase exploit engineering complexity. A vulnerability exploitable without a target-specific variable has a lower complexity than a vulnerability that would require non-trivial customization. This metric is meant to capture security mechanisms utilized by the vulnerable system.
Attack Requirements: This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. These differ from security-enhancing techniques/technologies (ref Attack Complexity) as the primary purpose of these conditions is not to explicitly mitigate attacks, but rather, emerge naturally as a consequence of the deployment and execution of the vulnerable system.
Privileges Required: This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. The method by which the attacker obtains privileged credentials prior to the attack (e.g., free trial accounts), is outside the scope of this metric. Generally, self-service provisioned accounts do not constitute a privilege requirement if the attacker can grant themselves privileges as part of the attack.
User interaction: This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. This metric determines whether the vulnerability can be exploited solely at the will of the attacker, or whether a separate user (or user-initiated process) must participate in some manner.
Vulnerable System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the VULNERABLE SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the VULNERABLE SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the VULNERABLE SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
Subsequent System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the SUBSEQUENT SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the SUBSEQUENT SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the SUBSEQUENT SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(38th percentile)

Weaknesses

Improper Neutralization of Input During Web Page Generation

The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. Learn more on MITRE.

CVE ID

CVE-2026-113654

GHSA ID

GHSA-x3q4-9hxx-gx8m

Source code

Loading Checking history
See something to contribute? Suggest improvements for this vulnerability.