Copyright © 2012 Red Hat, Inc. All rights reserved. Moderate 2026-07-06T21:15:45 showdown: Showdown: Stored Cross-Site Scripting via unescaped table header ID attributes in markdown 6.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N CWE-79

showdown contains a stored cross-site scripting vulnerability in the parseHeaders function of src/subParsers/makehtml/tables.js that fails to properly escape table header ID attributes. Attackers can inject arbitrary HTML and script-executing SVG elements through double-quote characters in markdown table headers, achieving stored XSS when untrusted markdown is rendered with the default github flavor configuration.

A flaw was found in Showdown. This vulnerability, a stored cross-site scripting (XSS) issue, allows an attacker to inject malicious code into web pages. By exploiting unescaped table header ID attributes in markdown, an attacker can embed arbitrary HTML and script-executing elements. When untrusted markdown is processed, this can lead to the execution of malicious scripts in a user's web browser, potentially compromising user data or session integrity.

Showdown, as integrated into Red Hat products, is susceptible to a stored cross-site scripting vulnerability. This flaw allows an attacker to inject arbitrary HTML and script-executing SVG elements by exploiting unescaped table header ID attributes within markdown. When untrusted markdown is rendered using the default GitHub flavor configuration, malicious scripts can execute in a user's web browser, potentially compromising data or session integrity. Affected versions: <= 2.1.0. To mitigate this vulnerability, avoid rendering untrusted markdown content within applications utilizing Showdown. If processing untrusted markdown is unavoidable, ensure that all input is thoroughly sanitized before rendering to prevent the injection of malicious HTML or script-executing elements. Cryostat 4 Fix deferred cryostat-openshift-console-plugin-npm Cryostat 4 Fix deferred showdown Multicluster Engine for Kubernetes Fix deferred multicluster-engine/console-mce-rhel9 Node HealthCheck Operator Fix deferred workload-availability/node-healthcheck-must-gather-rhel9 Node HealthCheck Operator Fix deferred workload-availability/node-healthcheck-operator-bundle Node HealthCheck Operator Fix deferred workload-availability/node-healthcheck-rhel9-operator Red Hat 3scale API Management Platform 2 Fix deferred 3scale-amp2/system-rhel7 Red Hat Advanced Cluster Management for Kubernetes 2 Fix deferred rhacm2/console-rhel9 Red Hat Ansible Automation Platform 2 Fix deferred automation-eda-controller Red Hat Ansible Automation Platform 2 Fix deferred automation-gateway Red Hat OpenShift AI (RHOAI) Fix deferred rhoai/odh-dashboard-rhel9 Red Hat OpenShift AI (RHOAI) Fix deferred rhoai/odh-mlflow-rhel9 Red Hat OpenShift AI (RHOAI) Fix deferred rhoai/odh-mod-arch-automl-rhel9 Red Hat OpenShift AI (RHOAI) Fix deferred rhoai/odh-mod-arch-autorag-rhel9 Red Hat OpenShift AI (RHOAI) Fix deferred rhoai/odh-mod-arch-eval-hub-rhel9 Red Hat OpenShift AI (RHOAI) Fix deferred rhoai/odh-mod-arch-gen-ai-rhel9 Red Hat OpenShift AI (RHOAI) Fix deferred rhoai/odh-mod-arch-maas-rhel9 Red Hat OpenShift AI (RHOAI) Fix deferred rhoai/odh-mod-arch-mlflow-rhel9 Red Hat OpenShift AI (RHOAI) Fix deferred rhoai/odh-mod-arch-model-registry-rhel9 Red Hat OpenShift Container Platform 4 Fix deferred openshift4/ose-console Red Hat OpenShift Container Platform 4 Fix deferred openshift4/ose-console-rhel9 Red Hat OpenShift Container Platform 4 Fix deferred openshift4/ose-monitoring-plugin-rhel8 Red Hat OpenShift Virtualization 4 Fix deferred container-native-virtualization/kubevirt-console-plugin Red Hat OpenShift Virtualization 4 Fix deferred container-native-virtualization/kubevirt-console-plugin-rhel9 Red Hat Quay 3 Fix deferred quay/quay-rhel8 Red Hat Quay 3 Fix deferred quay/quay-rhel9 https://www.cve.org/CVERecord?id=CVE-2026-59710 https://nvd.nist.gov/vuln/detail/CVE-2026-59710 https://github.com/showdownjs/showdown https://github.com/showdownjs/showdown/commit/e5cab1e9a5dcea2bb3cbf888863fa7e65ab37edf https://github.com/showdownjs/showdown/issues/1046 https://www.vulncheck.com/advisories/showdown-stored-xss-via-unescaped-table-header-id-attribute-injection