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CVE 2009-5031

ModSecurity before 2.5.11 treats request parameter values containing single quotes as files, which allows remote attackers to bypass filtering rules and perform other attacks such as cross-site scripting (XSS) attacks via a single quote in a request parameter in the Content-Disposition field of a request with a multipart/form-data Content-Type header.

See the CVE page on Mitre.org for more details.