The CAPTCHA implementation as used in (1) Francisco Burzi PHP-Nuke 7.0 and 8.1, (2) my123tkShop e-Commerce-Suite (aka 123tkShop) 0.9.1, (3) phpMyBitTorrent 1.2.2, (4) TorrentFlux 2.3, (5) e107 0.7.11, (6) WebZE 0.5.9, (7) Open Media Collectors Database (aka OpenDb) 1.5.0b4, and (8) Labgab 1.1 uses a code_bg.jpg background image and the PHP ImageString function in a way that produces an insufficient number of different images, which allows remote attackers to pass the CAPTCHA test via an automated attack using a table of all possible image checksums and their corresponding digit strings.

References

• https://nvd.nist.gov/vuln/detail/CVE-2008-2020
• https://exchange.xforce.ibmcloud.com/vulnerabilities/42152
• http://securityreason.com/securityalert/3834
• http://www.rooksecurity.com/blog/?p=6
• http://www.securityfocus.com/archive/1/491127/100/0/threaded
• http://www.securityfocus.com/bid/28877