External Web Application Vulnerability Scans (WAS)

External Web Application Vulnerability Scans (WAS) are used to identify security weaknesses in publicly accessible web applications. These scans evaluate applications from an external, unauthenticated perspective and are designed to detect common web-based vulnerabilities.

This article explains how WAS scans work, what they detect, how they are executed, and their limitations.

What External Web Application Vulnerability Scans Do

External Web Application Vulnerability Scans analyze publicly reachable web applications to identify weaknesses that could be exploited by an attacker over the internet.

These scans are commonly used to:

• Identify common web application vulnerabilities such as:

  • SQL Injection

  • Cross-Site Scripting (XSS)

  • Insecure headers and configurations

  • Input validation weaknesses

• Assess application-level exposure beyond port and service scanning

• Validate secure development and deployment practices

• Identify externally exploitable application risks

These scans evaluate only what is publicly accessible and do not authenticate to the application.

Execution Model

• Execution: Cyrisma cloud-based web scanning service

• Agent requirement: No local agent required

• Credential usage: None (unauthenticated by default)

Scans are executed from Cyrisma-managed external infrastructure and target publicly reachable web applications.

Firewall Allowlisting Requirements

To ensure Web Application Vulnerability Scans can reach your applications, firewalls, WAFs, and network security controls must allow inbound scanning traffic from Cyrisma’s web scanning infrastructure.

Web application scans may originate from the following IP addresses, which should be allowlisted where inbound filtering is enforced:

40.117.185.208
23.96.124.27
20.106.163.214

If traffic from these IP addresses is blocked, scan results may be incomplete or fail entirely.

Prerequisites

To run External Web Application Vulnerability Scans:

• The web application must be publicly accessible

• The application must be reachable over standard web protocols (HTTP/HTTPS)

• Firewalls or WAFs must allow inbound scanning traffic from Cyrisma scanning IPs

No agent installation or credential configuration is required.

Data Collected

External Web Application Vulnerability Scans collect publicly exposed application data only, including:

• Application endpoints and response behavior

• Input validation and error handling behavior

• HTTP headers and security configuration

• Evidence of common web vulnerabilities (e.g., XSS, injection flaws)

• SSL/TLS configuration and certificate details

The scan does not authenticate, modify data, or access backend systems.

Accuracy Considerations

Web application scans are effective for identifying common and known vulnerability patterns, but they have inherent constraints:

• Only unauthenticated areas of the application are assessed

• Vulnerabilities behind login pages are not detected

• Business-logic flaws may not be identified

• Results depend on application responses and behavior

These scans should be supplemented with authenticated testing or code review where deeper coverage is required.

Performance Considerations

Scan behavior may be influenced by:

• Application response times

• Rate-limiting or WAF behavior

• Application complexity and size

Web application scans are designed to be non-disruptive but may trigger security alerts if not allowlisted.

Common Limitations

• Only publicly accessible application components are scanned

• Authenticated functionality is not evaluated

• WAFs may block or alter scan traffic

• Results reflect application exposure at the time of scanning

Best Practices

• Allowlist Cyrisma web scanning IPs in firewalls and WAFs

• Run WAS scans regularly, especially after application changes

• Investigate high-severity findings promptly

• Correlate findings with development and deployment practices

• Use WAS as part of a broader vulnerability management program