CVE-2025-54880

### 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 following diagram and observe the modified DOM. ``` architecture-beta group api(cloud)[API] service db "<img src=x onerror=\"document.write(`xss on ${document.domain}`)\">" [Database] in api ``` Here is a PoC on mermaid.live: https://mermaid.live/edit#pako:eNo9T8FOwzAM_ZXI4rBJpWrpRtuIISF24caZZdKyxOsiLUnlJjCo-u9kQ8wX-_n5-dkjKK8ROEhSRxNQhUh4v8cghWMpOvKxZ7I3M3XyUc83L-9v2z9qQPo0CpneMwFPxnZsILU6M--QyNNKCAHaq2jRhfyL0vLZ7jwMiWd3443Q3krjpt38Mv4sgG3WMsi9HHDLjLs4CwcZdGQ08EARM7BISZMgjJdLBIQjWhTAU6nxIOMpCBBuSrJeug_v7b8yPdMdgR_kaUgo9loGXBvZkbS3LqHTSK8-ugC8LMrrEuAjnIEvlnlVL9q6rZu6Lh-rRQbfwKuyyZuybcvqIaWiqKcMfq6uRd7Uy-kXhYFzcA ### Impact XSS on all sites that use mermaid and render user supplied diagrams without further sanitization. ### Remediation Sanitize the value of `iconText` before passing it to `html()`.