The Browser Blind Spot: Why Your Security Stack Is Missing the Most Critical Attack Surface

A finance worker at a multinational engineering firm joined what looked like a routine video call with the CFO and senior leadership team.

Every face on the screen was real. Every voice matched perfectly.

Then they transferred $25 million to attackers.

Every participant on that call was an AI-generated deepfake. The attackers had cloned executive voices and faces using publicly available footage. The email security, network monitoring, and endpoint protection tools never raised a single alert. (Brightside AI)

This is what happens when your security stack cannot see inside the browser.

---

Table of contents

• The browser blind spot is real
• Why work moved into the browser
• Where traditional security tools fall short
• Threat categories inside the browser
• What is Browser Detection and Response
• Why ML and custom detection APIs matter
• How RedPhish delivers BDR today
• RedPhish in real world scenarios
• How RedPhish fits into your existing stack
• FAQs about browser detection and response

---

The browser blind spot is real

Security teams have email covered. They have network monitoring. They have endpoint detection. But they are missing the place where most attacks actually land.

Over 80% of phishing content is now AI-generated or AI-assisted. These attacks are grammatically perfect, contextually tailored, and translated instantly into any language. (Deepstrike)

In Q1 2025 alone, APWG observed over 1 million phishing attacks. That is the largest quarterly total in years. (APWG)

The browser is where these attacks succeed. A user clicks a link in email. Your email filter saw the message before delivery. Your network proxy saw the URL. But neither can see what happens after the page loads in the browser.

That is the blind spot.

![Close up view of laptop screen showing secure browser interface]

---

Why work moved into the browser

The shift to SaaS and remote work transformed the browser into the primary enterprise workspace.

By 2025, SaaS is projected to account for 85% of all business software. (SellersCommerce) Enterprises now manage an average of 275 SaaS applications. (Zylo)

Email, chat, CRM, project management, HR systems, and AI tools all run in the browser. People access sensitive data, authenticate to critical systems, and collaborate with external partners entirely through browser tabs.

But here is the problem. 48% of enterprise apps are shadow IT apps. These are applications employees use without the IT department's knowledge or approval. (SellersCommerce)

This creates a massive attack surface. Every SaaS login is a credential to steal. Every file upload is data to exfiltrate. Every AI prompt is sensitive information leaving your control.

And nearly all of this activity happens in the browser where traditional security tools have limited visibility.

![Person working on laptop with multiple browser tabs open]

---

Where traditional security tools fall short

Traditional security tools were built for different threats. They work well in their domains. But they have blind spots that attackers exploit daily.

Email security sees only pre-delivery

Email security scans messages before they reach inboxes. It catches known bad senders, malicious attachments, and suspicious links.

But phishing attacks have evolved. The vast majority of phishing attacks today use reverse proxies. They bypass most forms of MFA because sessions are created and stolen in real time as part of the attack. (Bleeping Computer)

Once a user clicks through to a phishing page, email security cannot see what happens next. The credential theft, session hijacking, and data exfiltration all happen in the browser.

Web gateways miss dynamic content

Web gateways and URL filters check destinations against blocklists. They block known bad domains.

But attackers use extensive redirect chains between the initial link and the actual phishing page. Every phishing page today comes with bot protection like custom CAPTCHAs or Cloudflare Turnstile to block security scanners. (Push Security)

MFA bypass and URL obfuscation were observed in 48% of phishing campaigns in 2025. CAPTCHA abuse appeared in 43%. (SiliconANGLE)

These techniques make it nearly impossible for URL-based filtering to catch threats before they reach users.

Endpoint security is one layer too low

EDR and endpoint protection excel at detecting malicious processes, file drops, and system changes. They stop malware that executes on the device.

But browser-based attacks often involve no file drops at all. Phishing pages harvest credentials through web forms. Session tokens are stolen from browser memory. DOM manipulation overlays fake login screens on legitimate pages.

SSE sees network traffic. DLP scans files. None of them inspect what is happening inside the session. They cannot see which SaaS tab is open, what data is being pasted, or which extension is injecting scripts. (The Hacker News)

The result is a parallel threat surface that traditional tools cannot reach.

![Abstract network security visualization with glowing nodes]

---

Threat categories inside the browser

Understanding browser-native threats helps explain why detection and response must move into the browser itself.

Multi-step and AI-enhanced phishing

Modern phishing pages are not static. They render content dynamically based on user interactions. They detect security scanners and show benign content. They personalize messages using AI with startling accuracy.

By October 2025, AI-generated phishing became the top enterprise email threat, surpassing ransomware, insider risk, and traditional social engineering combined. Security teams reported a 1,265% surge in phishing attacks linked to generative AI since 2023. (Brightside AI)

AI phishing attacks achieve a 60% overall success rate against humans. 54% of recipients click malicious links. That is nearly four times higher than traditional phishing campaigns. (Security Boulevard)

Malicious browser extensions

Browser extensions operate with extraordinary privileges. They can read passwords, modify web pages, and track every site you visit.

99% of enterprise users have at least one browser extension installed. 53% have extensions with "high" or "critical" risk permissions. These extensions can access cookies, passwords, browsing history, and webpage contents. (The Hacker News)

Over half (54%) of extension publishers are unknown and identified only via Gmail. 79% of publishers have released only one extension. (Help Net Security)

A single campaign called DarkSpectre affected over 8.8 million users across Chrome, Edge, and Firefox. The attackers spent seven years building trust before weaponizing their extensions. (The Hacker News)

Data exfiltration through legitimate SaaS

Attackers do not always need to build their own infrastructure. They can abuse legitimate SaaS and AI tools to exfiltrate data.

Over 20% of enterprise users have a GenAI extension installed. 58% of these have high or critical permissions. These tools can bypass corporate GenAI access controls and gain privileged access to sensitive data at twice the rate of other extensions. (Help Net Security)

IBM's 2024 report found that one out of every three data breaches now happens because of shadow IT. These breaches cost an average of $4.88 million each. (SellersCommerce)

Credential and session theft patterns

Phishing has evolved beyond simple fake login pages. Attackers now use consent phishing, device code phishing, and polymorphic extension attacks to steal sessions without ever touching credentials.

Consent phishing tricks victims into connecting malicious OAuth apps to their app tenant. Device code phishing authorizes through the device code flow to steal sessions. Malicious browser extensions steal credentials and cookies directly from the browser. (Push Security)

Polymorphic extension attacks allow malicious extensions to impersonate other extensions on your browser. The fake extension can look exactly like your password manager, crypto wallet, or banking app. (Bleeping Computer)

---

What is Browser Detection and Response

Browser Detection and Response (BDR) is the browser equivalent of EDR. It provides continuous behavioral visibility and real-time response capabilities inside the browser itself.

Think of EDR for your endpoints. It monitors processes, detects suspicious behavior, and responds to threats. BDR does the same thing for browser activity.

Core BDR capabilities

DOM and script monitoring: BDR watches what happens on web pages. It detects suspicious content injections, fake overlays, and malicious JavaScript behavior.

Credential prompt detection: BDR identifies when pages request credentials. It recognizes fake login forms, unapproved SSO prompts, and credential harvesting attempts.

Extension visibility: BDR monitors installed extensions, their permissions, and their behavior. It detects when extensions access sensitive data or communicate with suspicious servers.

Real-time response: BDR can block malicious pages, warn users about risks, and enforce security policies before damage occurs.

Rich telemetry: BDR feeds browser events to SIEM and SOAR platforms. Security teams get visibility into browser activity alongside endpoint, network, and email data.

BDR complements existing tools

BDR does not replace your email security, web gateway, or endpoint protection. It fills the gap they cannot reach.

Your email security catches phishing before delivery. BDR catches what happens when users click through anyway. Your web gateway blocks known bad URLs. BDR detects threats on pages that passed URL filtering. Your EDR stops malware on the endpoint. BDR stops attacks that never touch the filesystem.

Together, these tools create defense in depth that covers every stage of the attack chain.

![Modern office with computers showing security interface]

---

Why ML and custom detection APIs matter

Browser threats change too fast for static rules and blocklists. By the time a malicious domain hits a blocklist, attackers have already moved on.

The problem with static detection

Traditional security relies on indicators of compromise (IOCs). Block this URL. Flag this file hash. Quarantine this sender.

But phishing kits doubled in 2025 as attacks grew more evasive. New kits like Sneaky 2FA, Cephas, Whisper 2FA, and GhostFrame emerged. They use adversary-in-the-middle attacks, heavy JavaScript obfuscation, browser-in-the-browser techniques, and dynamic subdomain generation. (SiliconANGLE)

Signature-based detection cannot keep up with threats that change appearance on every request.

How ML changes detection

Machine learning enables detection based on behavior rather than signatures.

ML models learn what normal page structures look like. They learn typical user journeys through authentication flows. When something deviates from normal patterns, they flag it for review.

This matters because AI-generated phishing content is grammatically perfect and contextually aware. You cannot spot it by looking for spelling mistakes. But ML can detect that a credential prompt appeared in an unusual context, or that a page is mimicking a login form it should not have.

Custom Detection APIs for business rules

Every organization has unique security requirements. Approved SSO domains. High-risk applications. Sensitive data handling policies.

Custom Detection APIs let security teams encode these organization-specific rules. Instead of relying only on generic policies, teams can define what acceptable browser behavior looks like for their environment.

For example:

• Only allow credential submission to approved SSO domains
• Flag any attempt to paste sensitive data into unapproved SaaS apps
• Block extensions that request access to specific internal applications
• Alert when users authenticate to shadow IT services

This creates adaptive, policy-driven detection that evolves with your business.

---

How RedPhish delivers BDR today

RedPhish brings BDR capabilities to your browser without requiring you to rebuild your security stack.

ML-driven threat detection

RedPhish uses machine learning to detect browser-native threats that signature-based tools miss.

When you encounter a phishing page, RedPhish analyzes the page structure and behavior. It detects fake login overlays, credential harvesting forms, and session hijacking attempts regardless of what domain they appear on.

This is critical because attackers increasingly host phishing content on trusted platforms. The URL looks legitimate. The domain has good reputation. But the page behavior reveals malicious intent.

Custom Detection APIs

RedPhish provides APIs that let you encode your organization's security policies.

Define which SSO domains are approved for credential submission. Specify which SaaS applications employees can upload files to. Create rules for how sensitive data should be handled in the browser.

When users encounter situations that violate these policies, RedPhish can warn them, block the action, or log the event for security team review.

Extension and session visibility

RedPhish monitors browser extensions and sessions across your fleet.

It tracks which extensions are installed, what permissions they have, and how they behave. When an extension starts acting suspiciously, RedPhish flags it before data exfiltration occurs.

Real-time browser response

RedPhish does not just detect threats. It responds to them in real time.

• Block malicious pages before credentials are entered
• Warn users about suspicious credential prompts
• Prevent data paste into unapproved applications
• Disable compromised extensions automatically

Telemetry to SIEM and SOAR

RedPhish feeds rich browser telemetry to your security operations center.

Every detection, warning, and block is logged with context. Security analysts can correlate browser events with endpoint, network, and email data. SOAR playbooks can automate response based on browser signals.

---

RedPhish in real world scenarios

Here are concrete examples of how RedPhish protects against browser-native threats.

Scenario 1: AI-themed phishing on a trusted platform

Without RedPhish: An employee receives an email about accessing a new AI tool. The link points to a phishing page hosted on a legitimate cloud platform. The URL passes email filtering. The domain has good reputation. The employee enters their credentials. Attackers now have access to their account.

With RedPhish: The employee clicks the same link. RedPhish analyzes the page and detects an unapproved SSO prompt that mimics your organization's login. Before the employee can type their password, RedPhish blocks the page and explains why. The security team receives an alert with full context.

Scenario 2: Compromised extension update

Without RedPhish: An employee has a productivity extension installed for two years. The extension receives an update that adds data exfiltration code. The extension starts silently collecting session tokens and sending them to an external server. No security tool raises an alert because the extension was already approved.

With RedPhish: The extension update changes its behavior. RedPhish detects unusual data access patterns and network communication. It flags the extension as compromised and disables it before tokens are exfiltrated. The security team receives an alert to investigate.

Scenario 3: Sensitive data in unapproved AI app

Without RedPhish: An employee discovers a new AI assistant and starts using it to help with work tasks. They paste customer data, internal documents, and financial projections into the tool. The data leaves your control. You have no visibility into what was shared.

With RedPhish: The employee attempts to paste sensitive data into the unapproved AI app. RedPhish detects the action, intercepts it, and displays a just-in-time warning explaining the policy. The employee can proceed if the action is legitimate, or they can choose an approved alternative.

---

How RedPhish fits into your existing stack

RedPhish is designed to complement your existing security tools, not replace them.

Deployment

RedPhish deploys as a lightweight browser extension. No agent installation on endpoints. No network appliances to configure. Users can be up and running in minutes.

For enterprise deployment, RedPhish integrates with your MDM or group policy. Push the extension to managed browsers across your fleet.

Integration with SSO

RedPhish works with your existing SSO provider. It uses SSO authentication for user identification. Policies can be scoped to specific users, groups, or organizational units.

Integration with SIEM and SOAR

RedPhish sends detection events, user actions, and browser telemetry to your SIEM.

Security analysts can search and correlate browser events alongside other data sources. SOAR playbooks can trigger automated responses based on RedPhish signals.

Relationship to other tools

RedPhish sits between your users and the web, providing visibility that other tools cannot reach.

• Email security protects the inbox. RedPhish protects after the click.
• Web gateway filters URLs. RedPhish analyzes page behavior.
• EDR monitors the endpoint. RedPhish monitors the browser session.
• CASB controls SaaS access. RedPhish controls browser behavior within SaaS.

Together, these tools create layered protection across the entire attack surface.

![Team collaborating in modern office with security displays]

---

FAQs about browser detection and response

What is Browser Detection and Response (BDR)?

BDR is a security approach that provides continuous behavioral visibility and real-time response capabilities inside the browser. It monitors DOM changes, credential prompts, extension behavior, and user actions to detect and stop browser-native threats.

How does BDR differ from EDR?

EDR monitors endpoint processes, files, and system behavior. BDR monitors browser sessions, web page interactions, and browser extension activity. Both use behavioral analysis and real-time response, but they protect different parts of the attack surface.

How does BDR differ from a secure web gateway (SWG)?

SWGs filter web traffic based on URL categories, blocklists, and content inspection at the network layer. BDR analyzes what happens after pages load in the browser. SWG blocks known bad destinations. BDR detects threats that appear on any destination.

Does RedPhish replace my existing security tools?

No. RedPhish complements your existing email security, web gateway, endpoint protection, and CASB. It fills the visibility gap inside the browser where other tools cannot reach.

How does RedPhish detect attacks that do not match known signatures?

RedPhish uses machine learning to analyze page behavior and user interactions. Instead of matching against static blocklists, it detects anomalies in credential prompts, DOM manipulation, and data access patterns.

Can I customize RedPhish for my organization's policies?

Yes. RedPhish Custom Detection APIs let you encode organization-specific rules. Define approved SSO domains, restrict data sharing with specific applications, and create custom policies for your environment.

How does RedPhish handle privacy?

RedPhish uses privacy-first design with no unnecessary data retention. Detection happens locally in the browser. Only security-relevant events are logged and sent to your security operations center.

---

The browser is the new endpoint

Work happens in the browser now. Email, SaaS applications, AI tools, and sensitive data all live there.

Your security stack was built for a different world. Email filters, web proxies, and endpoint agents were designed before browser-based attacks became the primary threat vector.

Browser Detection and Response closes this gap. It brings visibility and response capabilities into the browser where attacks actually land.

RedPhish delivers BDR today. ML-driven detection catches threats that signature-based tools miss. Custom Detection APIs let you encode your organization's policies. Real-time response stops attacks before damage occurs.

Your users are already working in the browser. Your security should be there too.

Get started with RedPhish and protect your browser in minutes.