From $URL: Why was cpg1.5.12 released? The release covers a recently discovered input validation vulnerability that allows (if unpatched) a malevolent visitor to include own script routines (thread).
CVE-2011-3722 (http://nvd.nist.gov/nvd.cfm?cvename=CVE-2011-3722): Coppermine Photo Gallery (CPG) 1.5.12 allows remote attackers to obtain sensitive information via a direct request to a .php file, which reveals the installation path in an error message, as demonstrated by include/inspekt.php and certain other files.
Linking the two issues as they are both resolved by 1.5.20.
Thanks, Matti. I don't see any versions that were stable, so switching to ~4. Closing noglsa.