diff --git a/.changeset/brave-baths-behave.md b/.changeset/brave-baths-behave.md
new file mode 100644
index 000000000..b688a1faf
--- /dev/null
+++ b/.changeset/brave-baths-behave.md
@@ -0,0 +1,5 @@
+---
+'mermaid': patch
+---
+
+fix: Prevent HTML tags from being escaped in sandbox label rendering
diff --git a/cypress/helpers/util.ts b/cypress/helpers/util.ts
index 0332178f6..51268c2a9 100644
--- a/cypress/helpers/util.ts
+++ b/cypress/helpers/util.ts
@@ -98,12 +98,21 @@ export const openURLAndVerifyRendering = (
 
   cy.visit(url);
   cy.window().should('have.property', 'rendered', true);
-  cy.get('svg').should('be.visible');
-  // cspell:ignore viewbox
-  cy.get('svg').should('not.have.attr', 'viewbox');
 
-  if (validation) {
-    cy.get('svg').should(validation);
+  // Handle sandbox mode where SVG is inside an iframe
+  if (options.securityLevel === 'sandbox') {
+    cy.get('iframe').should('be.visible');
+    if (validation) {
+      cy.get('iframe').should(validation);
+    }
+  } else {
+    cy.get('svg').should('be.visible');
+    // cspell:ignore viewbox
+    cy.get('svg').should('not.have.attr', 'viewbox');
+
+    if (validation) {
+      cy.get('svg').should(validation);
+    }
   }
 
   if (screenshot) {
diff --git a/cypress/integration/rendering/flowchart-v2.spec.js b/cypress/integration/rendering/flowchart-v2.spec.js
index 5ef32c269..cd3676fbf 100644
--- a/cypress/integration/rendering/flowchart-v2.spec.js
+++ b/cypress/integration/rendering/flowchart-v2.spec.js
@@ -79,6 +79,18 @@ describe('Flowchart v2', () => {
       { htmlLabels: true, flowchart: { htmlLabels: true }, securityLevel: 'loose' }
     );
   });
+  it('6a: should render complex HTML in labels with sandbox security', () => {
+    imgSnapshotTest(
+      `flowchart TD
+    A[Christmas] -->|Get money| B(Go shopping)
+    B --> C{Let me think}
+    C -->|One| D[Laptop]
+    C -->|Two| E[iPhone]
+    C -->|Three| F[fa:fa-car Car]
+      `,
+      { securityLevel: 'sandbox', flowchart: { htmlLabels: true } }
+    );
+  });
   it('7: should render a flowchart when useMaxWidth is true (default)', () => {
     renderGraph(
       `flowchart TD
diff --git a/packages/mermaid/src/diagrams/common/common.spec.ts b/packages/mermaid/src/diagrams/common/common.spec.ts
index 3c7e0fdb8..edaf0b6dd 100644
--- a/packages/mermaid/src/diagrams/common/common.spec.ts
+++ b/packages/mermaid/src/diagrams/common/common.spec.ts
@@ -70,6 +70,31 @@ describe('Sanitize text', () => {
     });
     expect(result).not.toContain('javascript:alert(1)');
   });
+
+  it('should allow HTML tags in sandbox mode', () => {
+    const htmlStr = '<p>This is a <strong>bold</strong> text</p>';
+    const result = sanitizeText(htmlStr, {
+      securityLevel: 'sandbox',
+      flowchart: { htmlLabels: true },
+    });
+    expect(result).toContain('<p>');
+    expect(result).toContain('<strong>');
+    expect(result).toContain('</strong>');
+    expect(result).toContain('</p>');
+  });
+
+  it('should remove script tags in sandbox mode', () => {
+    const maliciousStr = '<p>Hello <script>alert(1)</script> world</p>';
+    const result = sanitizeText(maliciousStr, {
+      securityLevel: 'sandbox',
+      flowchart: { htmlLabels: true },
+    });
+    expect(result).not.toContain('<script>');
+    expect(result).not.toContain('alert(1)');
+    expect(result).toContain('<p>');
+    expect(result).toContain('Hello');
+    expect(result).toContain('world');
+  });
 });
 
 describe('generic parser', () => {
diff --git a/packages/mermaid/src/diagrams/common/common.ts b/packages/mermaid/src/diagrams/common/common.ts
index 444c9e930..a7b1e9ce8 100644
--- a/packages/mermaid/src/diagrams/common/common.ts
+++ b/packages/mermaid/src/diagrams/common/common.ts
@@ -66,7 +66,7 @@ export const removeScript = (txt: string): string => {
 const sanitizeMore = (text: string, config: MermaidConfig) => {
   if (config.flowchart?.htmlLabels !== false) {
     const level = config.securityLevel;
-    if (level === 'antiscript' || level === 'strict') {
+    if (level === 'antiscript' || level === 'strict' || level === 'sandbox') {
       text = removeScript(text);
     } else if (level !== 'loose') {
       text = breakToPlaceholder(text);