Cross-Site Scripting in ternary conditional operator

> ### Meta
> * CVSS: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N/E:F/RL:O/RC:C(5.0)
> * CWE-79

:information_source:  This vulnerability has been fixed in May 2019 already, CVE and GHSA were assigned later in October 2020

Problem

It has been discovered that the Fluid Engine (package typo3fluid/fluid) is vulnerable to cross-site scripting when making use of the ternary conditional operator in templates like the following.

{showFullName ? fullName : defaultValue}

Solution

Update to versions 2.0.5, 2.1.4, 2.2.1, 2.3.5, 2.4.1, 2.5.5 or 2.6.1 of this typo3fluid/fluid package that fix the problem described.

Updated versions of this package are bundled in following TYPO3 (typo3/cms-core) releases:

• TYPO3 v8.7.25 (using typo3fluid/fluid v2.5.5)
• TYPO3 v9.5.6 (using typo3fluid/fluid v2.6.1)

Credits

Thanks to Bill Dagou who reported this issue and to TYPO3 core merger Claus Due who fixed the issue.

References

• TYPO3-CORE-SA-2019-013