Lovable vs. Bolt vs. v0: Where AI App Builders Leave Security Gaps

A quick caveat: these tools ship updates constantly, and the security of any specific app depends far more on what you prompted and edited than on the builder's defaults. Treat the patterns below as "where to look first," not as fixed verdicts. Across all three, the same underlying truth holds — the model writes the visible feature and the happy path, and tends to skip the controls that only matter under misuse.

The short version

Lovable: Supabase RLS is the make-or-break

Lovable leans heavily on Supabase, which means the database is reachable directly from the browser via the anon key. The most consequential gap is therefore Row Level Security: tables created without RLS, or with permissive USING (true) policies, let one user read another's data. Lovable also tends to implement admin and permission checks in React while leaving the underlying query open.

• Check RLS on every tenant table and replace USING (true) with auth.uid()-scoped policies.
• Confirm the Supabase service-role key never reaches client code.
• Move admin and ownership checks to the server, not just the UI.

Bolt: rate limits, keys and webhooks

Bolt projects are typically Vite-based, so any variable exposed to the client lands in the shipped bundle — making leaked secret keys a recurring issue. Because Bolt happily wires up AI and API endpoints, the bigger operational gap is missing rate limits and usage caps. If the app charges money, webhook verification and idempotency are the parts most often left incomplete.

• Keep secret and service-role keys out of VITE_ variables; rotate anything committed.
• Add per-IP and per-account rate limits with hard usage ceilings on AI and upload routes.
• Verify webhook signatures against the raw body and make handlers idempotent.

v0: great UI, bring-your-own backend

v0 excels at Next.js front-end and component generation, but it often leaves the backend and data layer to you. That means the security story depends on how you wire server actions, route handlers and your database. The common gap is the boundary: UI state implies a permission that the server route never actually enforces, and NEXT_PUBLIC_ variables get used for things that shouldn't be public.

• Enforce auth and authorization inside every route handler and server action, not just in the component tree.
• Audit NEXT_PUBLIC_ variables — they ship to the browser.
• Validate inputs at the server boundary with a shared schema.

What they have in common

Strip away the stack differences and the same five issues dominate across Lovable, Bolt and v0: authorization that lives in the UI, secrets exposed to the client, ID-based routes without ownership checks, missing rate limits, and unverified payment webhooks. If you only have time for one pass before launch, review those five — in that order — regardless of which builder you used.

The practical upshot: pick the builder that fits your product and team, then run the same launch-readiness review on whatever it produces. The tool you choose changes which gap is most likely; it doesn't change the checklist.