showdownjs Showdown up to 2.1.0 Makehtml Link/Image Subparsers HTML injection

Summaryinfo

A vulnerability, which was classified as problematic, was found in showdownjs Showdown up to 2.1.0. The affected element is an unknown function of the component Makehtml Link/Image Subparsers. Executing a manipulation can lead to HTML injection. The identification of this vulnerability is CVE-2026-104477. The attack may be launched remotely. There is no exploit available.

Detailsinfo

A vulnerability classified as problematic was found in showdownjs Showdown up to 2.1.0. This vulnerability affects some unknown functionality of the component Makehtml Link/Image Subparsers. The manipulation with an unknown input leads to a html injection vulnerability. The CWE definition for the vulnerability is CWE-79. 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. As an impact it is known to affect integrity. CVE summarizes:

Showdown through 2.1.0 contains a cross-site scripting vulnerability in the makehtml link and image subparsers, which fail to escape double quotes in destination URLs placed into href and src attributes. Attackers can craft markdown links or images containing a double quote followed by onerror or onmouseover handlers to execute script when victims view rendered HTML.

The advisory is available at github.com. This vulnerability was named CVE-2026-104477 since 10/02/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. Successful exploitation requires user interaction by the victim. The technical details are unknown and an exploit is not available. The structure of the vulnerability defines a possible price range of USD $0-$5k at the moment (estimation calculated on 10/03/2026). This vulnerability is assigned to T1059.007 by the MITRE ATT&CK project.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

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Productinfo

Vendor

• showdownjs

Name

• Showdown

Version

• 2.0
• 2.1.0

Website

• Product: https://github.com/showdownjs/showdown/

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