Source code on a web server or repository often contains sensitive information and should generally not be accessible to users.
There are situations where it is critical to remove source code from an area or server. For example, obtaining Perl source code on a system allows an attacker to understand the logic of the script and extract extremely useful information such as code bugs or logins and passwords.

Primary

Implementation

Confidentiality
Read Application Data

Automated Static Analysis
Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)

Architecture and Design
System Configuration
Recommendations include removing this script from the web server and moving it to a location not accessible from the Internet.

The following code uses an include file to store database credentials:
database.inc

<?php$dbName = 'usersDB';$dbPassword = 'skjdh#67nkjd3$3$';?>

login.php

<?phpinclude('database.inc');$db = connectToDB($dbName, $dbPassword);$db.authenticateUser($username, $password);?>

If the server does not have an explicit handler set for .inc files it may send the contents of database.inc to an attacker without pre-processing, if the attacker requests the file directly. This will expose the database name and password.

The following comment, embedded in a JSP, will be displayed in the resulting HTML output.

<!-- FIXME: calling this with more than 30 args kills the JDBC server -->

CVE-2022-25512
Server for Team Awareness Kit (TAK) application includes sensitive tokens in the JavaScript source code.
https://www.cve.org/CVERecord?id=CVE-2022-25512

CVE-2022-24867
The LDAP password might be visible in the html code of a rendered page in an IT Asset Management tool.
https://www.cve.org/CVERecord?id=CVE-2022-24867

CVE-2007-6197
Version numbers and internal hostnames leaked in HTML comments.
https://www.cve.org/CVERecord?id=CVE-2007-6197

Allowed
This CWE entry is at the Base level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.
Carefully read both the name and description to ensure that this mapping is an appropriate fit. Do not try to 'force' a mapping to a lower-level Base/Variant simply to comply with this preferred level of abstraction.

Anonymous Tool Vendor (under NDA)
2006-07-19
Draft 3
2006-07-19

Eric Dalci
Cigital
2008-07-01
updated Time_of_Introduction

CWE Content Team
MITRE
2008-09-08
updated Relationships, Taxonomy_Mappings

CWE Content Team
MITRE
2008-10-14
updated Description

CWE Content Team
MITRE
2009-03-10
updated Relationships

CWE Content Team
MITRE
2011-03-29
updated Description, Name

CWE Content Team
MITRE
2011-06-01
updated Common_Consequences

CWE Content Team
MITRE
2012-05-11
updated Relationships

CWE Content Team
MITRE
2012-10-30
updated Potential_Mitigations

CWE Content Team
MITRE
2014-07-30
updated Relationships

CWE Content Team
MITRE
2017-11-08
updated Taxonomy_Mappings

CWE Content Team
MITRE
2020-02-24
updated Description, Name, Relationships, Type

CWE Content Team
MITRE
2021-10-28
updated Relationships

CWE Content Team
MITRE
2023-04-27
updated Relationships

CWE Content Team
MITRE
2023-06-29
updated Mapping_Notes

CWE Content Team
MITRE
2023-10-26
updated Demonstrative_Examples, Observed_Examples

CWE Content Team
MITRE
2025-12-11
4.19
2025-12-11
updated Applicable_Platforms, Detection_Factors, Relationships, Weakness_Ordinalities

Information Leak Through Source Code
Information Exposure Through Source Code