CVE-2026-59711
showdown - Cross-Site Scripting via Unescaped Metadata Title in completeHTMLDocument
Description
showdown contains a cross-site scripting vulnerability in metadata title handling that allows attackers to inject arbitrary HTML and JavaScript. When completeHTMLDocument option is enabled, unescaped less-than and greater-than characters in markdown frontmatter metadata are inserted directly into HTML title tags, enabling attackers to break out of the title context and execute malicious scripts in the rendered page.
INFO
Published Date :
July 6, 2026, 9:16 p.m.
Last Modified :
July 6, 2026, 9:16 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
Affected Products
The following products are affected by CVE-2026-59711
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
No affected product recoded yet
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | MEDIUM | 83251b91-4cc7-4094-a5c7-464a1b83ea10 | ||||
| CVSS 3.1 | MEDIUM | [email protected] | ||||
| CVSS 4.0 | MEDIUM | 83251b91-4cc7-4094-a5c7-464a1b83ea10 | ||||
| CVSS 4.0 | MEDIUM | [email protected] |
Solution
- Sanitize all user-supplied metadata content.
- Avoid direct insertion of metadata into HTML title tags.
- Update the showdown library to the latest version.
- Disable the completeHTMLDocument option if possible.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-59711.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-59711 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-59711
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-59711 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-59711 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
New CVE Received by [email protected]
Jul. 06, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'showdown', 'product': 'showdown', 'versions': [{'status': 'affected', 'version': '0', 'versionType': 'semver', 'lessThanOrEqual': '2.1.0'}], 'packageURL': 'pkg:npm/showdown', 'defaultStatus': 'unaffected'}] Added Description showdown contains a cross-site scripting vulnerability in metadata title handling that allows attackers to inject arbitrary HTML and JavaScript. When completeHTMLDocument option is enabled, unescaped less-than and greater-than characters in markdown frontmatter metadata are inserted directly into HTML title tags, enabling attackers to break out of the title context and execute malicious scripts in the rendered page. Added CVSS V4.0 AV:N/AC:L/AT:N/PR:N/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X Added CVSS V3.1 AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N Added CWE CWE-79 Added Reference https://github.com/showdownjs/showdown Added Reference https://github.com/showdownjs/showdown/issues/1047 Added Reference https://www.vulncheck.com/advisories/showdown-cross-site-scripting-via-unescaped-metadata-title-in-completehtmldocument