fix: stronger enforcement of normalizeLink (#6728)

Co-authored-by: dwelle <luzar.david@gmail.com>

src/data/url.test.tsx

@@ -0,0 +1,30 @@
+import { normalizeLink } from "./url";
+
+describe("normalizeLink", () => {
+  // NOTE not an extensive XSS test suite, just to check if we're not
+  // regressing in sanitization
+  it("should sanitize links", () => {
+    expect(
+      // eslint-disable-next-line no-script-url
+      normalizeLink(`javascript://%0aalert(document.domain)`).startsWith(
+        // eslint-disable-next-line no-script-url
+        `javascript:`,
+      ),
+    ).toBe(false);
+    expect(normalizeLink("ola")).toBe("ola");
+    expect(normalizeLink(" ola")).toBe("ola");
+
+    expect(normalizeLink("https://www.excalidraw.com")).toBe(
+      "https://www.excalidraw.com",
+    );
+    expect(normalizeLink("www.excalidraw.com")).toBe("www.excalidraw.com");
+    expect(normalizeLink("/ola")).toBe("/ola");
+    expect(normalizeLink("http://test")).toBe("http://test");
+    expect(normalizeLink("ftp://test")).toBe("ftp://test");
+    expect(normalizeLink("file://")).toBe("file://");
+    expect(normalizeLink("file://")).toBe("file://");
+    expect(normalizeLink("[test](https://test)")).toBe("[test](https://test)");
+    expect(normalizeLink("[[test]]")).toBe("[[test]]");
+    expect(normalizeLink("<test>")).toBe("<test>");
+  });
+});