Upgrade to version 1.2.8 or higher, as it has been reported to fix this vulnerability. An upgrade is required as there are no known workarounds.
Vendor URL: http://www.punbb.org/
Vendor Specific News/Changelog Entry: http://www.punbb.org/changelogs/1.2.7_to_1.2.8.txt
Secunia Advisory ID:16908
Related OSVDB ID: 19617