# Cursor App Rescue: 7 Problems to Fix Before Launch
> Built with Cursor and working on your machine? The 7 problems to check before real users arrive, from leaked keys and open API routes to fake packages.
Canonical: https://app369.com/blog/cursor-app-rescue-2026/
Last updated: 2026-10-22
[ **Simon Dziak** Founder & developer, App369](https://app369.com/about/szymon-dziak/) [LinkedIn](https://www.linkedin.com/in/szymondziak/)
Published October 20, 2026 · Updated October 22, 2026•Facts last verified October 22, 2026•9 min
App369https://app369.com/blog/cursor-app-rescue-2026/
[← Back to Blog](https://app369.com/blog/)
## Key takeaways
- →Cursor's own review guide warns that "AI-generated code can look correct but be subtly wrong," and that "Passing tests don't guarantee the code works correctly."
- →In Next.js, "A page-level authentication check does not extend to the Server Actions defined within it," so every action and API route has to check the user itself.
- →Any variable starting with NEXT_PUBLIC_ "will be inlined into any JavaScript sent to the browser," so a secret key there is public.
- →A 2024 study found at least 5.2% of packages suggested by commercial models, and 21.7% by open-source models, did not exist. Check every new dependency before you install it.
- →Cursor's workspace trust is "disabled by default", and older Cursor versions had MCP flaws that allowed code to run on your machine, so keep Cursor updated.
Pricing an app? Try the free [app cost calculator](https://app369.com/tools/app-cost-calculator/) or get a range for your project in the [instant quote](https://app369.com/instant-quote/).
**Cursor writes code in your own repository, so the problems that show up with real users are ordinary web app problems that are easy to miss without a review: secret keys, unprotected endpoints, open database rules, unchecked packages and settings that differ between your machine and the host.** Unlike Lovable, Bolt or Replit, Cursor doesn’t host your app or pick your database. That gives you more control, and it also means no platform check runs before you launch.
Below are the seven problems to check before launch, how to test each one, and how to fix it. The facts come from Cursor’s documentation and forum, the Next.js, Vercel, Supabase and Firebase docs, OWASP, NVD and one research paper, and I re-read each source on October 22, 2026. The examples use Next.js, but the checks apply to any stack. The how-to-check and how-to-fix steps are my own advice.
## 1. Secret keys in the browser or in git
In Next.js, a variable whose name starts with `NEXT_PUBLIC_` “will be inlined into any JavaScript sent to the browser.” If the agent puts a secret there to make a feature work, every visitor can read it. Supabase is blunt about its secret keys: “A secret key bypasses every Row Level Security policy you have. Never put one in a browser, a shipped application, or source control.”
Cursor can also read your `.env` file. A Cursor staff reply on its forum explains that `.env*` is in the default ignore list, “but that list only applies to indexing”, and Cursor’s docs say the terminal and MCP tools used by the Agent “cannot block access to code governed by `.cursorignore`”.
**How to check:** search the code and the git history for `service_role`, `sb_secret_`, `sk_live` and your providers’ key prefixes. List every `NEXT_PUBLIC_` variable and ask whether each one is safe to publish. Open the JavaScript your live site loads and search it for the same prefixes.
**How to fix:** rotate every key that was ever in browser code or git, move secrets to server-only code and the host’s environment settings, and keep production secrets out of the project folder.
## 2. API routes and server actions anyone can call
Hiding a button doesn’t protect the action behind it. The Next.js data security guide says a Server Action “is reachable via a direct POST request, not just through your application’s UI,” and that “A page-level authentication check does not extend to the Server Actions defined within it.” OWASP calls the related flaw insecure direct object reference (IDOR): attackers “access or modify objects by manipulating identifiers”, such as changing an ID in a request to read another user’s record.
**How to check:** for every API route and every `'use server'` function, confirm it checks the session and that the record belongs to that user. Call each one while logged out, then as user B with user A’s IDs.
**How to fix:** check authentication and ownership inside each handler, or in one server-only data layer that every handler uses. Return only the fields the screen needs, and deny by default.
## 3. Database rules left wide open
If the browser talks to the database directly, the rules are the only thing standing between a stranger and your data. Supabase says: “Enable RLS on every table in an exposed schema.” Firebase’s own example of an open rule set carries the warning “**NEVER** use this rule set in production; it allows anyone to overwrite your entire database,” and says that without authentication and rules, “anyone who guesses your project ID can steal, modify, or delete the data.”
A quick way to make a permission error go away during development is to turn row-level security off or add a rule that lets everyone in. That shortcut is easy to forget before launch. Already turned RLS on? See [why data can still be exposed with RLS on](https://app369.com/fix/supabase-rls-enabled-still-exposed/).
**How to check:** on Supabase, open the Security Advisor and search your policies for `using ( true )`, or paste them into the free [Supabase RLS policy checker](https://app369.com/tools/supabase-rls-policy-checker/). On Firebase, search your rules for `if true` and for test-mode dates, or paste the file into the free [Firebase Security Rules checker](https://app369.com/tools/firebase-rules-checker/). Then read and write as a logged-out visitor and as a second user. If your app uses Supabase from the browser, the free scan at the end of this page does the logged-out read test for you.
**How to fix:** turn on RLS for every exposed table with policies tied to the signed-in user, write Firebase rules that check `request.auth`, and keep secret or admin keys on the server. The [Firebase security guide](https://app369.com/blog/firebase-security-guide-2026/) has worked examples.
**Supabase’s October 30 change.** If your app uses Supabase, from October 30, 2026 new tables in existing projects are no longer granted to the `anon`, `authenticated` and `service_role` roles automatically, so a table the agent adds after that date returns a “permission denied” error until it is granted. Paste your migrations into the free [Supabase October 30 grants checker](https://app369.com/tools/supabase-oct-30-checker/) to see which tables need grants.
## 4. Packages that don’t exist, or aren’t what they seem
Code models sometimes suggest packages that were never published. A 2024 study of 16 code models found “the average percentage of hallucinated packages is at least 5.2% for commercial models and 21.7% for open-source models.” Those figures cover models in general, not Cursor in particular. The risk is that someone registers an invented name with harmful code, and the next install pulls it in.
**How to check:** read every new line in `package.json` or `requirements.txt`. Confirm each package exists on its registry, has a real history and the publisher you expect. Run your package manager’s audit and commit the lockfile.
**How to fix:** remove anything you can’t account for, install only after checking the registry, and read what the Agent wants to install before you approve it, and don’t rely on Cursor’s approval prompts alone.
## 5. Big edits that look right and aren’t
Cursor’s own guide to reviewing agent code says “AI-generated code can look correct but be subtly wrong,” and “Passing tests don’t guarantee the code works correctly,” because the tests may check the wrong behavior. It recommends small commits, each one a single logical change, so a person can review them.
**How to check:** read the full diff before you accept it, then run the main user flows by hand: sign-up, sign-in, payment and anything that writes data. Look at which tests cover sign-in, payments and data changes.
**How to fix:** ask for one change at a time, commit small, and add tests for the money, login and data paths. Test with a second account and realistic data, not only the demo user.
## 6. Works locally, fails on the host
The `.env` file on your machine is not on your host. In Next.js, `NEXT_PUBLIC_` values are fixed when the app is built: “After being built, your app will no longer respond to changes to these environment variables.” Vercel adds that “Any change you make to environment variables are not applied to previous deployments, they only apply to new deployments.”
**How to check:** list every `process.env` value the code reads and confirm each one is set on the host for production and for previews. Check whether any were added after the last deploy.
**How to fix:** set every variable on the host, redeploy, read server-only values only on the server, and add a startup check that fails loudly when a required value is missing.
## 7. An out-of-date editor and unknown MCP servers
The editor itself is part of the risk. NVD lists [CVE-2025-54136](https://nvd.nist.gov/vuln/detail/CVE-2025-54136), where in Cursor “versions 1.2.4 and below, attackers can achieve remote and persistent code execution” by swapping an already-approved MCP configuration for a malicious command (fixed in 1.3), and [CVE-2025-64109](https://nvd.nist.gov/vuln/detail/CVE-2025-64109), where opening a cloned repository in the Cursor CLI Beta could run a malicious MCP server “without any warning”. Cursor’s security page also says “Cursor supports workspace trust, but it’s disabled by default,” and calls its run controls “best-effort guardrails rather than a hard security boundary.”
**How to check:** confirm Cursor is on the current version, open `.cursor/mcp.json` in any repository you cloned, and list the MCP servers you have approved.
**How to fix:** update Cursor, remove MCP servers you don’t recognize, turn on workspace trust, and open repositories you don’t trust in a plain text editor first.
## What to do this week
1. Search the code, git history and live JavaScript for secret keys, and rotate anything you find.
2. Call every API route and server action while logged out and as a second user.
3. Check your database rules, or run the free leak scan below if your app uses Supabase.
4. Check every package added in the last month against its registry.
5. Compare the host’s environment variables with your local `.env`, then redeploy.
## After the fixes: can Google and AI assistants read it?
Check one thing before you announce it: open your live page, view the page source (not the inspector), and search for a sentence from your page. If it isn’t there, the text only appears after JavaScript runs. Google renders JavaScript, but [Vercel’s December 2024 crawler study](https://vercel.com/blog/the-rise-of-the-ai-crawler) found that OpenAI’s, Anthropic’s and Perplexity’s crawlers (GPTBot, OAI-SearchBot, ChatGPT-User, ClaudeBot and PerplexityBot) don’t, so those crawlers see a page with no text, and an assistant that relies on them can’t quote it. If search matters for this app, the [SEO, GEO and AEO page](https://app369.com/service/seo-geo-aeo/) explains what makes a site readable for Google and AI assistants, and the [$750 AI Search Visibility Audit](https://app369.com/fixed-price/ai-search-visibility-audit/) checks it for you.
## Need a hand?
For a free first look, enter your live app’s address in the [AI app security check](https://app369.com/tools/ai-app-check/). It flags secret keys shipped in your JavaScript and missing security headers in a few seconds, without logging in or touching your database.
If you’d rather have someone else check it, the [AI-Built App Rescue](https://app369.com/fixed-price/ai-app-rescue/) starts with a $450 Launch Check. You send read-only access, and within 3 business days you get each problem ranked by severity, with where it is and how it was confirmed, plus a fixed price for the Rescue Sprint. The $450 is credited if you go ahead, and you keep the code either way. Built with an app builder instead? See the [Lovable](https://app369.com/blog/lovable-app-rescue-2026/), [Bolt](https://app369.com/blog/bolt-app-rescue-2026/), [Replit](https://app369.com/blog/replit-app-rescue-2026/), [Base44](https://app369.com/blog/base44-app-rescue-2026/) and [v0](https://app369.com/blog/v0-app-rescue-2026/) checklists. Or [send me a short description](https://app369.com/contact/).
On Supabase? The [Supabase security review before launch](https://app369.com/blog/supabase-security-review-before-launch-2026/) covers every Supabase setting to check, with an order for fixing them. Comparing who should do the work? [Hiring someone to finish a vibe-coded app](https://app369.com/blog/hire-developer-finish-vibe-coded-app-2026/) compares freelancers, agencies, builder partners and fixed-price checks, with 10 questions to ask before you hire.
## **Is your app leaking data?**
Scan your live Supabase project for tables anyone can read with the public key your site already ships. Built for Lovable, Bolt and hand-built apps. The scan only asks whether each table has rows a logged-out visitor can see. It never fetches, stores or shows a row.
## **Want this done at a fixed price?**
Fixed scope, fixed price, paid upfront. The work happens in writing; no call needed.
- [**AI-Built App Rescue**from $450A Lovable, Bolt or Cursor app checked end to end in 3 days, then its worst problems fixed at a fixed price.](https://app369.com/fixed-price/ai-app-rescue/)
- [**Firebase Security Rules Audit + Fix PR**$950Tests whether one user can read or edit another customer’s data, and fixes what it finds.](https://app369.com/fixed-price/firebase-security-rules-audit/)
- [**AI Agent Engineering Setup**from $750Your repos made ready for Claude Code, Codex and Cursor agents: a written diagnostic first, then a setup sprint.](https://app369.com/fixed-price/ai-agent-engineering-setup/)
## **Frequently asked questions**
- **Is code written by Cursor safe to launch?**
- It can be, once a person has reviewed it. Cursor itself says AI-generated code can look correct but be subtly wrong, and that passing tests do not prove it works. Review the diff, test the main flows by hand and test access with two accounts.
- **Can Cursor read my .env file?**
- It can. A Cursor staff reply on its forum says the default ignore list only applies to indexing, not to Agent tool calls, and Cursor's docs say the terminal and MCP tools cannot block access to files in .cursorignore. Keep production secrets out of the project folder.
- **Why does my Cursor app work locally but not after deploying?**
- Usually because an environment variable exists in your local .env file but not on the host, or was set after the last build. In Next.js, NEXT_PUBLIC_ values are fixed at build time, and on Vercel a variable change only applies to new deployments, so redeploy after changing one.
- **Does the free leak scan work for apps built with Cursor?**
- Only if the app uses Supabase from the browser. The scan checks the public Supabase key your live site ships. For Firebase, a custom backend or server-only data access, use the two-account and logged-out tests on this page instead.
- **Do I keep my code if I hire someone to fix my Cursor app?**
- Yes. A Cursor project is ordinary code in your own repository, so a developer works from that repository and you keep everything.
## **Sources**
1. [Cursor docs, Reviewing agent code](https://cursor.com/learn/reviewing-testing)
2. [Cursor docs, Agent security](https://cursor.com/docs/agent/security)
3. [Cursor docs, Ignore files](https://cursor.com/docs/reference/ignore-file)
4. [Cursor forum, Cursor reads .env files by default](https://forum.cursor.com/t/cursor-reads-env-files-by-default/152167)
5. [Next.js docs, Data security](https://nextjs.org/docs/app/guides/data-security)
6. [Next.js docs, Environment variables](https://nextjs.org/docs/app/guides/environment-variables)
7. [Vercel docs, Environment variables](https://vercel.com/docs/environment-variables)
8. [OWASP, Insecure Direct Object Reference Prevention Cheat Sheet](https://cheatsheetseries.owasp.org/cheatsheets/Insecure_Direct_Object_Reference_Prevention_Cheat_Sheet.html)
9. [Supabase docs, Row Level Security](https://supabase.com/docs/guides/database/postgres/row-level-security)
10. [Supabase docs, API keys](https://supabase.com/docs/guides/getting-started/api-keys)
11. [Firebase docs, Avoid insecure rules](https://firebase.google.com/docs/firestore/security/insecure-rules)
12. [Spracklen et al., We Have a Package for You! (arXiv 2406.10279)](https://arxiv.org/abs/2406.10279)
13. [NVD, CVE-2025-54136](https://nvd.nist.gov/vuln/detail/CVE-2025-54136)
14. [NVD, CVE-2025-64109](https://nvd.nist.gov/vuln/detail/CVE-2025-64109)
15. [Supabase GitHub discussions, Data API grants change (October 30, 2026)](https://github.com/orgs/supabase/discussions/45329)
16. [Supabase docs, Securing your API (default privileges)](https://supabase.com/docs/guides/api/securing-your-api)
Tags
#cursor app rescue #fix cursor app #cursor ai code review #cursor security #next.js server actions security #supabase row level security #firebase security rules #ai app rescue #vibe coded app
Generated from app369.com . © 2026 App369. All rights reserved.
**Share:**
[Share on Twitter](https://twitter.com/intent/tweet?text=Cursor%20App%20Rescue%3A%207%20Problems%20to%20Fix%20Before%20Launch&url=https%3A%2F%2Fapp369.com%2Fblog%2Fcursor-app-rescue-2026%2F) [Share on LinkedIn](https://www.linkedin.com/sharing/share-offsite/?url=https%3A%2F%2Fapp369.com%2Fblog%2Fcursor-app-rescue-2026%2F) [Share on Facebook](https://www.facebook.com/sharer/sharer.php?u=https%3A%2F%2Fapp369.com%2Fblog%2Fcursor-app-rescue-2026%2F)
## **Related Resources **
[Lovable App Rescue: 7 Problems to Fix Before Launch](https://app369.com/blog/lovable-app-rescue-2026/) [Supabase Security Review Before Launch (2026)](https://app369.com/blog/supabase-security-review-before-launch-2026/) [Bolt App Rescue: 8 Problems to Fix Before Launch](https://app369.com/blog/bolt-app-rescue-2026/) [v0 App Rescue: 8 Problems to Fix Before Launch](https://app369.com/blog/v0-app-rescue-2026/) [Base44 App Rescue: 8 Problems to Fix Before Launch](https://app369.com/blog/base44-app-rescue-2026/) [Replit App Rescue: 7 Problems to Fix Before Launch](https://app369.com/blog/replit-app-rescue-2026/)
## **Related guides **
[**Replit App Rescue: 7 Problems to Fix Before Launch**
Your Replit app works in the workspace but breaks after you publish. The 7 problems to check first, from missing secrets to vanishing uploads.**Read more **](https://app369.com/blog/replit-app-rescue-2026/) [**Firebase Security Rules Best Practices: The Complete Guide (2026)**
Firebase security rules best practices for 2026 in one table: deny-all baseline, update checks, custom claims, validation, emulator tests and Cloud Functions.** Read more **](https://app369.com/blog/firebase-security-guide-2026/)