Failing to properly validate user input, the form component is susceptible to Arbitrary File Disclosure. A valid backend user account is needed to exploit this vulnerability. Only forms are vulnerable, which contain upload fields.

References

• https://github.com/FriendsOfPHP/security-advisories/blob/master/typo3/cms/2016-04-12-2.yaml
• https://typo3.org/security/advisory/typo3-core-sa-2016-010