SQL::Abstract versions from 1.90_01 before 2.000001_04 for Perl allow SQL injection via the where values of a nested statement in an identifier position.
A nested statement such as { -select => ... } in a position where plain scalars are identifiers treats its own plain scalars as identifiers too. These positions are the select list, ORDER BY, GROUP BY, RETURNING, and with the ExtraClauses plugin FROM (-as) and JOIN (to). The values of the statement's where, having and set clauses, and the rows of a -values, go into the SQL text instead of the bind list, unescaped unless quote_char is set. Subselects in a WHERE condition are not affected.
An application that passes untrusted input as a where value of such a nested statement, expecting it to be bound, allows SQL injection.
Upgrade to SQL-Abstract 2.000001_04 or later.