CVE-2014-2861 in Commonspot Content Server
Summary
by MITRE
Incomplete blacklist vulnerability in PaperThin CommonSpot before 7.0.2 and 8.x before 8.0.3 allows remote attackers to conduct cross-site scripting (XSS) attacks via a crafted string, as demonstrated by bypassing a protection mechanism that removes only the "alert" string.
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Analysis
by VulDB Data Team • 05/10/2026
The vulnerability identified as CVE-2014-2861 represents a critical incomplete blacklist security flaw in PaperThin CommonSpot content management system versions prior to 7.0.2 and 8.x versions before 8.0.3. This vulnerability stems from inadequate input validation mechanisms that fail to properly sanitize user-supplied data before processing or rendering within web applications. The flaw specifically manifests when the system attempts to protect against cross-site scripting attacks by removing known malicious strings such as "alert" from user input, but this protection mechanism is insufficient and easily bypassed through creative input manipulation.
The technical nature of this vulnerability aligns with CWE-79, which describes cross-site scripting flaws where untrusted data is improperly sanitized before being rendered in web pages. Attackers can exploit this weakness by crafting malicious input strings that circumvent the simplistic blacklist filtering approach. The bypass occurs because the protection mechanism only targets specific patterns like "alert" while ignoring other potentially harmful JavaScript code sequences or encoding variations that could achieve the same malicious objectives. This incomplete filtering approach demonstrates a fundamental misunderstanding of secure input validation principles where relying solely on blacklists creates inherent security gaps.
Operationally, this vulnerability enables remote attackers to execute arbitrary JavaScript code within the context of affected web applications, potentially leading to session hijacking, credential theft, or redirection to malicious sites. The impact extends beyond simple XSS exploitation as attackers can leverage this vulnerability to establish persistent access to affected systems, particularly when the compromised application handles sensitive user data or administrative functions. The vulnerability affects web applications built on PaperThin CommonSpot that process user input through the affected versions, creating a significant attack surface for malicious actors seeking to compromise web applications.
Organizations should immediately implement comprehensive input validation measures that move beyond simple blacklist approaches to adopt more robust security practices including proper encoding, whitelisting of acceptable input patterns, and thorough sanitization of all user-supplied data. The mitigation strategy should include updating to the patched versions of PaperThin CommonSpot as specified in the advisory, implementing additional security layers such as web application firewalls, and conducting thorough security assessments of all web applications built on this platform. This vulnerability also highlights the importance of following secure coding practices as outlined in the OWASP Top Ten and NIST cybersecurity guidelines, particularly regarding input validation and output encoding to prevent injection attacks.