fix: sanitize GitHub username inputs

src/app/api/compare/route.ts

@@ -6,15 +6,13 @@ import {
   resolveLocale,
 } from "@/features/comparison/services";
 import { formatApiErrorResponse, parseSelectedLanguagesFromSearchParams } from "@/lib/api";
+import { cleanGitHubUsername } from "@/utils/github";
 
 export const runtime = "nodejs";
 
 export async function GET(request: Request) {
   const { searchParams } = new URL(request.url);
-  const usernames = searchParams
-    .getAll("username")
-    .map((username) => username.trim())
-    .filter(Boolean);
+  const usernames = searchParams.getAll("username").map(cleanGitHubUsername).filter(Boolean);
 
   if (usernames.length !== 2) {
     return NextResponse.json(

src/app/api/user/[username]/route.ts

@@ -1,12 +1,13 @@
 import { NextResponse } from "next/server";
 import { getUserProfile } from "@/features/developer/services";
 import { formatApiErrorResponse, parseSelectedLanguagesFromSearchParams } from "@/lib/api";
+import { cleanGitHubUsername } from "@/utils/github";
 
 export const runtime = "nodejs";
 
 export async function GET(request: Request, { params }: { params: Promise<{ username: string }> }) {
   const { username } = await params;
-  const trimmed = username?.trim();
+  const trimmed = cleanGitHubUsername(username ?? "");
 
   if (!trimmed) {
     return NextResponse.json(

src/features/comparison/components/compare-form.tsx

@@ -9,6 +9,7 @@ import { Card, CardContent, CardDescription, CardHeader, CardTitle } from "@/com
 import { useTranslation } from "@/components/providers/language-provider";
 import { handleEscapeToClear, matchesHotkey, useHotkeys, useIsApplePlatform } from "@/hooks";
 import { cn } from "@/utils/cn";
+import { cleanGitHubUsername } from "@/utils/github";
 
 const LANGUAGE_OPTIONS = [
   "TypeScript",
@@ -115,7 +116,7 @@ export function CompareForm({
 
   const submitComparison = () => {
     if (!canSubmit) return;
-    onSubmit(username1.trim(), username2.trim(), {
+    onSubmit(cleanGitHubUsername(username1), cleanGitHubUsername(username2), {
       selectedLanguages,
     });
   };

src/features/comparison/tests/compare-form.test.tsx

@@ -10,7 +10,19 @@ vi.mock("@/components/providers/language-provider", () => ({
   useTranslation: () => ({ t: (key: string) => key }),
 }));
 
-function ControlledForm({ initial1 = "", initial2 = "" }) {
+function ControlledForm({
+  initial1 = "",
+  initial2 = "",
+  onSubmit = () => {},
+}: {
+  initial1?: string;
+  initial2?: string;
+  onSubmit?: (
+    username1: string,
+    username2: string,
+    options: { selectedLanguages: string[] },
+  ) => void;
+}) {
   const [username1, setUsername1] = useState(initial1);
   const [username2, setUsername2] = useState(initial2);
   const [selectedLanguages, setSelectedLanguages] = useState<string[]>([]);
@@ -25,7 +37,7 @@ function ControlledForm({ initial1 = "", initial2 = "" }) {
         setUsername1={setUsername1}
         setUsername2={setUsername2}
         setSelectedLanguages={setSelectedLanguages}
-        onSubmit={() => {}}
+        onSubmit={onSubmit}
       />
     </>
   );
@@ -89,4 +101,20 @@ describe("CompareForm / shortcut", () => {
       "/",
     );
   });
+
+  test("submits cleaned GitHub usernames", async () => {
+    const user = userEvent.setup();
+    const onSubmit = vi.fn();
+    render(
+      <ControlledForm
+        initial1=" @octocat "
+        initial2="https://github.com/torvalds/"
+        onSubmit={onSubmit}
+      />,
+    );
+
+    await user.click(screen.getByRole("button", { name: "form.compare" }));
+
+    expect(onSubmit).toHaveBeenCalledWith("octocat", "torvalds", { selectedLanguages: [] });
+  });
 });

src/features/comparison/tests/compare.route.test.ts

@@ -216,6 +216,24 @@ describe("GET /api/compare", () => {
     expect(body.winner?.username).toBe("user-a");
   });
 
+  test("cleans GitHub handles and profile URLs before loading users", async () => {
+    mocks.getUserData.mockResolvedValue({
+      data: makeUser("octocat", "The Octocat"),
+      metrics: { duration: 0, errors: [] },
+    });
+    mocks.calculateUserScore.mockReturnValue(makeScore(10));
+
+    const response = await GET(
+      makeRequest({
+        username: [" @octocat ", "https://github.com/torvalds/"],
+      }),
+    );
+
+    expect(response.status).toBe(200);
+    expect(mocks.getUserData).toHaveBeenNthCalledWith(1, "octocat", expect.any(Object));
+    expect(mocks.getUserData).toHaveBeenNthCalledWith(2, "torvalds", expect.any(Object));
+  });
+
   test("returns null percentage when the losing final score is zero", async () => {
     mocks.getUserData.mockResolvedValueOnce({
       data: makeUser("user-a", "User A"),

src/features/developer/tests/user.route.test.ts

@@ -150,6 +150,23 @@ describe("GET /api/user/[username]", () => {
     expect(body.location).toBe("Stockholm, Sweden");
   });
 
+  test("cleans a GitHub profile URL before loading the user", async () => {
+    const rawUser = makeUser("octocat", "The Octocat");
+    mocks.getUserData.mockResolvedValueOnce({
+      data: rawUser,
+      metrics: { duration: 100, errors: [] },
+    });
+    mocks.calculateUserScore.mockReturnValueOnce(makeScore(40));
+
+    const request = new Request("http://localhost/api/user/https%3A%2F%2Fgithub.com%2Foctocat%2F");
+    const response = await GET(request, {
+      params: Promise.resolve({ username: "https://github.com/octocat/" }),
+    });
+
+    expect(response.status).toBe(200);
+    expect(mocks.getUserData).toHaveBeenCalledWith("octocat", expect.any(Object));
+  });
+
   test("returns 404 when user is not found on GitHub", async () => {
     mocks.getUserData.mockRejectedValueOnce(
       new GitHubApiError({

src/utils/github.test.ts

@@ -0,0 +1,14 @@
+import { describe, expect, test } from "vitest";
+import { cleanGitHubUsername } from "./github";
+
+describe("cleanGitHubUsername", () => {
+  test.each([
+    [" @octocat ", "octocat"],
+    ["https://github.com/octocat/", "octocat"],
+    ["github.com/torvalds", "torvalds"],
+    ["octocat/", "octocat"],
+    ["https://example.com/octocat", "https://example.com/octocat"],
+  ])("cleans %j", (input, expected) => {
+    expect(cleanGitHubUsername(input)).toBe(expected);
+  });
+});

src/utils/github.ts

@@ -0,0 +1,20 @@
+export function cleanGitHubUsername(input: string): string {
+  const trimmed = input.trim().replace(/^@+/, "").replace(/\/+$/, "");
+  if (!trimmed) return "";
+
+  const url = tryParseGitHubUrl(trimmed);
+  if (!url) return trimmed;
+
+  return url.pathname.split("/").filter(Boolean)[0] ?? "";
+}
+
+function tryParseGitHubUrl(input: string): URL | null {
+  const urlInput = input.startsWith("github.com/") ? `https://${input}` : input;
+
+  try {
+    const url = new URL(urlInput);
+    return url.hostname === "github.com" || url.hostname === "www.github.com" ? url : null;
+  } catch {
+    return null;
+  }
+}

src/utils/index.ts

@@ -1 +1,2 @@
 export * from "./cn";
+export * from "./github";