Mermaid does not properly sanitize architecture diagram iconText leading to XSS
Date: 2025-08
Affected: npm/mermaid
Attack vector: xss
Category: vulnerability-disclosure
Severity: Medium
CVE: CVE-2025-54880
CWE: CWE-79

### Summary In the default configuration of mermaid 11.9.0, user supplied input for architecture diagram icons is passed to the d3 `html()` method, creating a sink for cross site scripting. ### Details Architecture diagram service `iconText` values are passed to the d3 `html()` method, allowing malicious users to inject arbitrary HTML and cause XSS when mermaid-js is used in it's default configuration. The vulnerability lies here: ```ts export const drawServices = async function ( db: ArchitectureDB, elem: D3Element, services: ArchitectureService[] ): Promise<number> { for (const service of services) { /** ... **/ } else if (service.iconText) { bkgElem.html( `<g>${await getIconSVG('blank', { height: iconSize, width: iconSize, fallbackPrefix: architectureIcons.prefix })}</g>` ); const textElemContainer = bkgElem.append('g'); const fo = textElemContainer .append('foreignObject') .attr('width', iconSize) .attr('height', iconSize); const divElem = fo .append('div') .attr('class', 'node-icon-text') .attr('style', `height: ${iconSize}px;`) .append('div') .html(service.iconText); // <- iconText passed into innerHTML /** ... **/ }; }; ``` This issue was introduced with 734bde38777c9190a5a72e96421c83424442d4e4, around 15 months ago, which was released in [v11.1.0](https://github.com/mermaid-js/mermaid/releases/tag/mermaid%4011.1.0). ### PoC Render the foll


Mitigations:

Architectural layers (MAESTRO):