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10 Common Vulnerabilities in Web Applications (and How to Avoid Them)

Auteur n°2 – Jonathan

By Jonathan Massa
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Summary – Several vulnerabilities (SQL and NoSQL injections, exposure of sensitive data, misconfigurations, flawed access and authentication controls, XSS/CSRF, RFI) jeopardize the confidentiality, integrity, and reputation of web applications. Without server-side validation, robust encryption, RBAC/MFA, and automated configuration management, each flaw can become a critical entry point.
Solution: adopt continuous “shift-left” security with ORM/parameterized queries, AES-256, secure CI/CD, SAST/DAST scans, and regular pentests.

Web applications are constantly exposed to a variety of threats. A single weak point can lead to data breaches, financial losses, or lasting damage to an organization’s reputation. Cybersecurity is not just a box to tick at the end of a project: it must be designed and implemented from the outset and maintained throughout the application lifecycle. Regular testing and rigorous best practices are essential to ensure that the smallest flaw does not become a critical incident.

Vulnerabilities Related to Data and Injections

These flaws allow the execution of malicious code and the theft of sensitive data. A single unfiltered request can compromise the entire system.

Injection (SQL, NoSQL, Commands)

Injection occurs when an attacker manages to insert malicious code into a query, whether it’s SQL, NoSQL queries, or system commands. The input field is not properly sanitized, and the backend interprets this content as an instruction.

Once exploited, it becomes possible to extract credentials, modify or delete records, and even gain full access to the database or server. The consequences range from data theft to service disruption.

To prevent this risk, it is imperative to use parameterized queries or an Object-Relational Mapping (ORM) that strictly separates code from data. All user input must undergo strict server-side validation.

Implementing strong authentication for database calls, limiting the privileges of application accounts, and conducting regular code reviews are integral to a secure development discipline.

Sensitive Data Exposure

Data exposure occurs when sensitive information, unencrypted or poorly protected, is accessible to an attacker. It can result from improper local storage, clear-text transmission, or faulty encryption key management.

Without encryption of data at rest and in transit, secrets (passwords, API keys, customer information) become easy prey for automated scripts or network interceptions.

Example: A Swiss SME in financial services discovered that an unencrypted data archive stored on a test server had been indexed by an internal search engine. This incident exposed thousands of customer files, demonstrating the importance of disabling caching in non-production environments and systematically encrypting all critical information.

Adopting robust encryption (AES-256 or higher), managing keys via a hardware security module (HSM) or a secure cloud service, and removing obsolete data residues are essential best practices.

Security Misconfiguration

Security misconfiguration manifests as unnecessarily exposed services, open ports, default passwords, or outdated components. It’s one of the most common flaws in web applications.

Every server or framework comes with default security settings that are often unsuitable for production. Excessive permissions, overly verbose log files, or unprotected admin tools expand the attack surface.

To avoid this, disable unnecessary modules, restrict access to sensitive directories, and implement an automated deployment policy that ensures identical configurations across environments.

Continuous monitoring of dependencies and versions, coupled with automated vulnerability scans, allows teams to correct configuration drift before it becomes critical.

Access Control, Authentication, and Direct References

Faulty mechanisms can grant unauthorized access to resources or accounts. These errors expose business processes and critical data.

Broken Access Control

Broken access control allows an illegitimate user to modify data, access sensitive resources, or perform forbidden operations. Relying solely on client-side restrictions is ineffective without server-side enforcement.

Poor implementation of roles and permissions can lead to privilege escalation, granting a user or attacker access to administrator-only functions.

To guard against this, implement a Role-Based Access Control (RBAC) or Attribute-Based Access Control (ABAC) model, verify permissions on every API call, and document authorized actions for each user profile.

Regular penetration tests, simulating different privilege levels, ensure that any changes to roles or endpoints do not introduce security regressions.

Broken Authentication

Broken authentication allows an attacker to impersonate a legitimate user. It often stems from poorly managed sessions, weak hashing algorithms, or lack of multi-factor authentication.

Without MFA (Multi-Factor Authentication) and with outdated hashing functions (MD5, SHA-1), stolen credentials can be reused or sessions hijacked via fixation attacks.

Example: A public health organization suffered account takeovers due to unlimited login attempts and unsalted password hashes. This incident highlighted the importance of implementing temporary lockouts after multiple failures and using Argon2 or bcrypt for password storage.

Implement session timeouts, enforce password rotations, and deploy multi-factor authentication everywhere to drastically reduce this risk.

Insecure Direct Object Reference (IDOR)

IDOR occurs when an internal resource (file, record, endpoint) is referenced directly by a predictable or manipulable identifier in the URL or payload.

By simply changing a numeric or alphanumeric parameter, an attacker can access other users’ information or alter customer data without authorization.

To prevent this, validate each request on the server by comparing the provided identifier with the authenticated user’s permissions. Non-sequential tokens or UUIDs make it harder for an attacker to guess valid references.

API audits and analysis of request logs quickly detect brute-force attempts or resource enumeration, alerting teams to abnormal activity.

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Script-Based Attacks and Cross-Site Requests

XSS and CSRF attacks exploit browser trust and manipulate user sessions. Unvalidated redirects facilitate phishing and malware distribution.

Cross-Site Scripting (XSS)

XSS occurs when an attacker injects malicious script into a page viewed by other users. This script runs in the victim’s browser and can hijack sessions, steal cookies, or redirect to fraudulent sites.

Without strict output encoding and input sanitization, any user-input field becomes an injection point. Modern frameworks may include protections, but they must be properly configured.

Example: A Swiss e-commerce platform saw users redirected to a fake payment form after exploiting an XSS vulnerability in its search field. This attack underscored the importance of enforcing a strict Content Security Policy (CSP) and consistently encoding all dynamic data.

Sanitize inputs with trusted libraries, encode HTML and JavaScript outputs, and enable security headers like CSP to prevent XSS.

Cross-Site Request Forgery (CSRF)

CSRF tricks an authenticated user into performing an unwanted action on a web application where they’re logged in. The browser automatically sends session cookies, facilitating the malicious request.

Without anti-CSRF tokens or custom header checks, a simple instruction in an email or on a third-party site can trigger critical operations (password change, fund transfer, data deletion).

Using synchronized tokens (stored in the server session and validated on each sensitive request) and verifying request origins (SameSite cookies, referer header) are effective safeguards.

Combining CSRF tokens with MFA for high-risk actions further enhances application resilience.

Unvalidated Redirects

An unvalidated or open redirect allows an attacker to send users from a legitimate link to a malicious site. The user follows the redirect in good faith and may fall victim to phishing.

Some applications accept a dynamic redirect parameter without validation. Simply replacing the destination URL can trap the victim.

To secure these flows, compare every redirect URL against a whitelist or validate it with a strict regex. Limit dynamic destinations to approved domains.

Alerts triggered by multiple or chained redirects help detect sophisticated hijacking attempts.

Remote File Inclusion (RFI)

RFI allows malicious external code to execute within the application. This vulnerability is common in default PHP configurations.

Understanding RFI

Remote File Inclusion occurs when an application accepts an external URL to load a script or template without verification. The server then downloads arbitrary code and executes it in its context.

PHP directives like allow_url_include, if not disabled, open the door to RFI attacks. An attacker can host a malicious payload and link it to the target application.

Unlike injection attacks, RFI exploits the language’s file inclusion functionality, enabling attackers to introduce new malicious features at runtime.

Impact and Consequences

In an RFI scenario, external code can exfiltrate data, install a web shell, modify web pages, or redirect traffic. Attackers often gain full server access.

Shared or multi-tenant environments are especially vulnerable if filesystem permissions aren’t isolated. A successful RFI on one site can compromise multiple applications on the same server.

Consequences include loss of control, disruption of continuous deployment, and malware distribution to end users. Automated bots routinely scan the internet for this weakness.

Remediating RFI is often complex: you must review the architecture, correct configurations, and verify the integrity of every included component.

Prevention and Best Practices

The first line of defense is disabling remote file inclusion in the language configuration (set allow_url_include to off in PHP). Files to be included should originate from a local, validated source.

Implement a strict whitelist of authorized files, control file extensions, and verify package signatures to prevent calls to unapproved external resources.

Filesystem permission isolation and the use of containers limit the blast radius in case of compromise. Each component should run in a restricted environment without broad write permissions.

Finally, automated security scans—including RFI detection via DAST tools—quickly identify permissive configurations and trigger alerts before exploitation.

Turn Your Web Application Security into a Competitive Advantage

Continuous integration of security best practices—input validation, data encryption, robust access controls, and automated testing—is key to significantly reducing risks. A holistic strategy that combines Static Application Security Testing (SAST), Dynamic Application Security Testing (DAST), Interactive Application Security Testing (IAST), and regular penetration tests ensures enhanced resilience against evolving threats.

Regardless of your industry or organization size, anticipating web vulnerabilities and fixing flaws before they’re exploited minimizes remediation costs, protects your reputation, and maintains stakeholder trust. Our experts are ready to help you develop a pragmatic, customized approach aligned with your business objectives.

Discuss your challenges with an Edana expert

By Jonathan

Technology Expert

PUBLISHED BY

Jonathan Massa

As a senior specialist in technology consulting, strategy, and delivery, Jonathan advises companies and organizations at both strategic and operational levels within value-creation and digital transformation programs focused on innovation and growth. With deep expertise in enterprise architecture, he guides our clients on software engineering and IT development matters, enabling them to deploy solutions that are truly aligned with their objectives.

FAQ

Frequently Asked Questions about Web Vulnerabilities

How do you plan the management of web vulnerabilities in a custom project?

Planning starts with an initial audit to identify data flows and potential entry points. Then, you set up a testing schedule (SAST, DAST, penetration tests) and code review milestones. Each phase includes security acceptance criteria (e.g. test coverage, remediation of critical vulnerabilities). This modular, iterative approach ensures risk traceability and allows adjusting the scope according to business context.

Which indicators should be tracked to evaluate the effectiveness of penetration tests?

Key KPIs include the number and severity of discovered vulnerabilities, average time to fix, vulnerability recurrence by category, and coverage of critical components. You can also measure the success rate of automated versus manual tests and remediation time by vulnerability type. These indicators provide an objective view of progress and guide development priorities.

What is the difference between SAST, DAST, and IAST for securing an application?

SAST analyzes source code before execution to detect vulnerability patterns, DAST tests the application in production via external requests to spot runtime flaws, and IAST combines both by instrumenting the code during runtime. Each covers a different spectrum: SAST early in the cycle, DAST for black-box security, and IAST for continuous feedback in CI/CD.

How can you anticipate risks related to SQL and NoSQL injections?

It is imperative to separate code and data using parameterized queries or an ORM. Each user input must be validated and filtered server-side with whitelists. Application accounts should have minimal privileges. Finally, include targeted code reviews of queries and regularly run automated injection tests to detect abnormal behavior before production.

What are common mistakes in security configuration?

Recurring mistakes include leaving default passwords, exposing development ports, not disabling unused modules, and keeping overly verbose logs unprotected. Omitting security headers (CSP, HSTS) or failing to automate deployments multiplies the risk of configuration drift. The golden rule: favor automation and continuous monitoring.

How do you integrate data encryption into an existing application?

Start by inventorying sensitive data (passwords, customer information) and choose a proven algorithm (AES-256). Use a key management system (HSM or cloud service) and gradually encrypt data at rest and in transit. Adapt your code to decrypt on the server side only when needed, and test in a preproduction environment before final deployment.

What criteria should you use to choose between open source and commercial solutions?

Assess total cost of ownership (maintenance, licenses, support), community maturity and size, and compatibility with your stack. Open source tools often offer more flexibility and auditability, while commercial solutions may provide SLA-backed support and turnkey features. The choice will depend on security requirements, your internal capabilities, and project criticality.

What methodological framework should be used to maintain security in production?

Adopt a DevSecOps approach: integrate SAST in CI, DAST in preproduction, and IAST in staging. Define a patch and incident management process. Automate dependency scans and security log monitoring. Complement with annual penetration tests and periodic code reviews. This continuous approach ensures active monitoring and rapid response to emerging threats.

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