fix: target blank removed from anchor tag

cypress/integration/rendering/classDiagram.spec.js

@@ -501,4 +501,16 @@ describe('Class diagram', () => {
         B : -methods()
       `);
   });
+
+  it('should handle notes with anchor tag having target attribute', () => {
+    renderGraph(
+      `classDiagram
+        class test { }
+        note for test "<a href='https://mermaid.js.org/' target="_blank"><code>note about mermaid</code></a>"`
+    );
+
+    cy.get('svg').then((svg) => {
+      cy.get('a').should('have.attr', 'target', '_blank').should('have.attr', 'rel', 'noopener');
+    });
+  });
 });

packages/mermaid/src/diagrams/common/common.spec.ts

@@ -38,6 +38,20 @@ describe('when securityLevel is antiscript, all script must be removed', () => {
     compareRemoveScript(`<img onerror="alert('hello');">`, `<img>`);
   });
 
+  it('should detect unsecured target attribute, if value is _blank then generate a secured link', () => {
+    compareRemoveScript(
+      `<a href="https://mermaid.js.org/" target="_blank">note about mermaid</a>`,
+      `<a href="https://mermaid.js.org/" target="_blank" rel="noopener">note about mermaid</a>`
+    );
+  });
+
+  it('should detect unsecured target attribute from links', () => {
+    compareRemoveScript(
+      `<a href="https://mermaid.js.org/" target="_self">note about mermaid</a>`,
+      `<a href="https://mermaid.js.org/" target="_self">note about mermaid</a>`
+    );
+  });
+
   it('should detect iframes', () => {
     compareRemoveScript(
       `<iframe src="http://abc.com/script1.js"></iframe>

packages/mermaid/src/diagrams/common/common.ts

@@ -25,7 +25,27 @@
  * @returns The safer text
  */
 export const removeScript = (txt: string): string => {
-  return DOMPurify.sanitize(txt);
+  const TEMPORARY_ATTRIBUTE = 'data-temp-href-target';
+
+  DOMPurify.addHook('beforeSanitizeAttributes', (node: Element) => {
+    if (node.tagName === 'A' && node.hasAttribute('target')) {
+      node.setAttribute(TEMPORARY_ATTRIBUTE, node.getAttribute('target') || '');
+    }
+  });
+
+  const sanitizedText = DOMPurify.sanitize(txt);
+
+  DOMPurify.addHook('afterSanitizeAttributes', (node: Element) => {
+    if (node.tagName === 'A' && node.hasAttribute(TEMPORARY_ATTRIBUTE)) {
+      node.setAttribute('target', node.getAttribute(TEMPORARY_ATTRIBUTE) || '');
+      node.removeAttribute(TEMPORARY_ATTRIBUTE);
+      if (node.getAttribute('target') === '_blank') {
+        node.setAttribute('rel', 'noopener');
+      }
+    }
+  });
+
+  return sanitizedText;
 };
 
 const sanitizeMore = (text: string, config: MermaidConfig) => {