OWASP Top 10: Building Secure Next.js Applications
A practical guide to the most critical web application security vulnerabilities and how to prevent them in your Next.js projects.
Why Security Cannot Be an Afterthought
Most security breaches exploit basic vulnerabilities that were never fixed. As a developer who builds production systems for businesses, I treat security as a core deliverable — not an optional extra.
1 — Broken Access Control
Never trust the client. Always verify permissions server-side.
import { getServerSession } from "next-auth"
export async function GET() {
const session = await getServerSession()
if (!session || session.user.role !== "admin") {
return new Response("Forbidden", { status: 403 })
}
}2 — Injection Attacks
Never build SQL queries by concatenating strings.
// Vulnerable — never do this
const query = `SELECT * FROM users WHERE email = "${email}"`
// Safe — parameterised query
const user = await db.query("SELECT * FROM users WHERE email = $1", [email])3 — Validate All Inputs Server-Side
import { z } from "zod"
const Schema = z.object({
name: z.string().min(2).max(100),
email: z.string().email(),
message: z.string().min(10).max(2000),
})
export async function POST(req: Request) {
const result = Schema.safeParse(await req.json())
if (!result.success) {
return NextResponse.json({ error: result.error.flatten() }, { status: 400 })
}
}4 — Hash Passwords Properly
import bcrypt from "bcryptjs"
const hash = await bcrypt.hash(password, 12)
const valid = await bcrypt.compare(inputPassword, storedHash)5 — Keep Dependencies Updated
pnpm audit
pnpm audit --fixConclusion
Security is not a feature you add at the end — it is a discipline you practice from the first line of code. If you need a security audit of your existing application, reach out.
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