Bolt
security
Insecure Cookie Configuration in Bolt Application
Your Bolt.new application stores authentication tokens or session data in cookies without proper security attributes. Missing HttpOnly, Secure, and SameSite flags leave your users' sessions vulnerable to theft through XSS attacks, man-in-the-middle interception, and cross-site request forgery.
When Bolt generates authentication code, it may set cookies using basic document.cookie assignments or use a cookie library with default (insecure) settings. This means session tokens can be read by JavaScript (enabling XSS-based theft), transmitted over unencrypted HTTP connections, and sent along with cross-site requests.
An attacker who steals a session cookie can impersonate any user on your platform, access their data, make purchases on their behalf, or escalate privileges to admin accounts. This is a silent vulnerability that leaves no trace until it's exploited.
Error Messages You Might See
Warning: Cookie set without HttpOnly flag
Cookie rejected due to SameSite=None without Secure
Set-Cookie header ignored: must be Secure when SameSite=None
Mixed Content: cookie will be blocked in future browser versions
Common Causes
- Missing HttpOnly flag — Cookies are readable by JavaScript via document.cookie, so any XSS vulnerability can steal session tokens
- Missing Secure flag — Cookies are sent over unencrypted HTTP connections, allowing interception on public WiFi networks
- SameSite not set to Strict or Lax — Cookies are sent with cross-site requests, enabling CSRF attacks
- Cookies set from client-side JavaScript — Using document.cookie or js-cookie instead of setting cookies from the server with proper flags
- Overly broad cookie domain or path — Cookies scoped to a parent domain or root path, making them accessible to other subdomains or paths that may be compromised
How to Fix It
- Set cookies from the server — Use Set-Cookie headers from your API routes instead of document.cookie: res.setHeader('Set-Cookie', `token=${value}; HttpOnly; Secure; SameSite=Lax; Path=/; Max-Age=86400`)
- Enable HttpOnly — This prevents JavaScript from accessing the cookie, blocking XSS-based theft entirely
- Enable Secure flag — Ensures cookies are only sent over HTTPS connections, preventing interception
- Set SameSite to Lax or Strict — Lax allows cookies on top-level navigations (links), Strict blocks all cross-site cookie sending
- Use a session library — Install iron-session or next-auth which handle secure cookie configuration by default
- Set proper expiration — Use Max-Age or Expires instead of session cookies for persistent login, and set reasonable timeouts
Real developers can help you.
Richard McSorley
Full-Stack Software Engineer with 8+ years building high-performance applications for enterprise clients. Shipped production systems at Walmart (4,000+ stores), Cigna (20M+ users), and Arkansas Blue Cross. 5 patents in retail/supply chain tech. Currently focused on AI integrations, automation tools, and TypeScript-first architectures.
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As a Product Engineer at Klasio, I contributed to end-to-end product development, focusing on scalability, performance, and user experience.
My work spanned building and refining core features, developing dynamic website templates, integrating secure and reliable payment gateways, and optimizing the overall system architecture.
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ISHANTDEEP SINGH
Senior Software Engineer with 7+ years of experience in React, JavaScript, TypeScript, Next.js, and Node.js. I’ve also worked as a tech lead for startups, owning end-to-end technical execution including architecture, development, scaling, and delivery. I bring a strong mix of hands-on coding, product thinking, and technical leadership, and I’m comfortable building products from scratch as well as improving and scaling existing systems.
Caio Rodrigues
I'm a full-stack developer focused on building practical and scalable web applications. My main experience is with **React, TypeScript, and modern frontend architectures**, where I prioritize clean code, component reusability, and maintainable project structures.
I have strong experience working with **dynamic forms, state management (Redux / React Hook Form), and complex data-driven interfaces**. I enjoy solving real-world problems by turning ideas into reliable software that companies can actually use in their daily operations.
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Basel Issmail
’m a Senior Full-Stack Developer and Tech Lead with experience designing and building scalable web platforms. I work across the full development lifecycle, from translating business requirements into technical architecture to delivering reliable production systems.
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Matthew Butler
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rayush33
JavaScript (React.js, React Native, Node.js) Developer with demonstrated industry experience of 4+ years, actively looking for opportunities to hone my skills as well as help small-scale business owners with solutions to technical problems
Milan Surelia
Milan Surelia is a Mobile App Developer with 5+ years of experience crafting scalable, cross-platform apps at 7Span and Meticha. At 7Span, he engineers feature-rich Flutter apps with smooth performance and modern UI. As the Co-Founder of Meticha, he builds open-source tools and developer-focused products that solve real-world problems.
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🎯 Revamped the Vepaar app into Vepaar Store & CRM with a 2x performance boost and smoother UX.
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Dor Yaloz
SW engineer with 6+ years of experience,
I worked with React/Node/Python
did projects with React+Capacitor.js for ios
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Get HelpFrequently Asked Questions
What is the difference between HttpOnly, Secure, and SameSite?
HttpOnly prevents JavaScript access to the cookie (blocks XSS theft). Secure ensures the cookie is only sent over HTTPS. SameSite controls whether cookies are sent with cross-site requests (blocks CSRF). You need all three for proper security.
Should I use localStorage or cookies for auth tokens?
Cookies with HttpOnly and Secure flags are safer for auth tokens because JavaScript cannot access them, making XSS attacks ineffective. localStorage is readable by any script on the page, so a single XSS vulnerability exposes all tokens.