CVE-2013-1955 in Easy PHP Calendar
Summary
by MITRE
Multiple cross-site scripting (XSS) vulnerabilities in (1) index.php and (2) datePicker.php in Easy PHP Calendar 6.x and 7.x before 7.0.13 allow remote attackers to inject arbitrary web script or HTML via unspecified vectors.
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Analysis
by VulDB Data Team • 02/12/2018
The vulnerability identified as CVE-2013-1955 represents a critical cross-site scripting flaw affecting Easy PHP Calendar versions 6.x and 7.x prior to 7.0.13. This security weakness manifests in two primary files within the application's codebase: index.php and datePicker.php, making it a widespread concern for users of these calendar applications. The vulnerability classification aligns with CWE-79 which specifically addresses Cross-Site Scripting vulnerabilities, where improper input validation allows malicious actors to inject client-side scripts into web applications. These XSS vulnerabilities create a significant attack surface that can be exploited by remote threat actors without requiring any privileged access or authentication.
The technical exploitation of this vulnerability occurs through unspecified input vectors that allow attackers to inject malicious web scripts or HTML content directly into the calendar application's output. When users view affected pages, the injected scripts execute in their browsers, potentially leading to session hijacking, credential theft, or redirection to malicious websites. The flaw exists because the application fails to properly sanitize or escape user-supplied input before rendering it in web pages, creating an environment where attacker-controlled data can be interpreted as executable code rather than benign text. This type of vulnerability typically arises from inadequate output encoding practices and insufficient validation of user inputs across multiple application entry points.
The operational impact of CVE-2013-1955 extends beyond simple script injection, as it can enable sophisticated attack chains that leverage the compromised calendar application as a pivot point for broader network infiltration. Attackers can craft malicious payloads that persist in the calendar application's data storage, affecting all users who subsequently access the compromised pages. The vulnerability's presence in both index.php and datePicker.php indicates a systemic issue in the application's input handling architecture, suggesting that similar flaws may exist in other components. This vulnerability directly maps to several techniques described in the MITRE ATT&CK framework under the T1059.002 sub-technique for Command and Scripting Interpreter, where adversaries leverage web application vulnerabilities to execute malicious scripts in victim browsers.
Mitigation strategies for this vulnerability require immediate application of the vendor-provided patch version 7.0.13 or later, which addresses the input validation gaps in both affected files. Organizations should implement comprehensive input sanitization measures that enforce strict output encoding for all user-supplied data, particularly when rendering content in web interfaces. The remediation process should include thorough code reviews focusing on HTML output generation and input validation routines across all application components. Additionally, implementing Content Security Policy (CSP) headers can provide an additional layer of protection by restricting the sources from which scripts can be executed, effectively limiting the impact of successful XSS attacks even if other defenses fail. Regular security assessments and vulnerability scanning should be conducted to identify similar input validation weaknesses that may exist in other application components, ensuring comprehensive protection against similar attack vectors.