Oracle Application Express - APEX Security

APEX Security

There is a common misconception that the abstracted nature of APEX applications results in a relatively secure user environment. However, APEX applications suffer from the same classes of application security flaws as other web applications based on more direct technologies such as PHP, ASP.net and Java.

The main classes of vulnerability that affect APEX applications are: SQL injection, Cross-site scripting (XSS), and Access Control.

APEX applications inherently use PL/SQL constructs as the base server-side language. As well as accessing data via PL/SQL blocks, an APEX application will use PL/SQL to implement authorization, and to conditionally display web page elements. This means that generally APEX applications suffer from SQL injection when these PL/SQL blocks do not correctly validate and handle malicious user input. Oracle implemented a special variable type for APEX called Substitution Variables (with a syntax of &NAME.) and these are not safe and lead to SQL Injection. Where the injection occurs within a PL/SQL block an attacker can inject an arbitrary number of queries or statements to execute.

Cross-Site Scripting vulnerabilities arise in APEX applications just like other web application languages. Oracle provide the htf.escape_sc function to escape user data that is displayed within a rendered HTML response. The reports that APEX generates also provide protection against XSS through the Display As setting on report columns. Originally the default was for reports to be created without any escaping of the columns, although recent versions now set the column type to escape by default. Column definitions can be queried programmatically to check for columns that do not escape the value.

To control access to resources within an APEX application a developer can assign authorization schemes to resources (such as pages and items). These must be applied consistently in order to ensure that resources are appropriately protected. A typical example of inconsistent access-control being applied is where an authorization scheme is set for a Button item, but not the associated Process that is performed when the button is clicked. A malicious user can perform the process (through JavaScript) without requiring the actual Button to be accessible.

Since APEX 4.0, the Application Builder interface provides some limited assessment of the security posture through the Advisor utility.

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