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Apache Struts 2 Documentation
S2-023
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## Summary

Generated value of token can be predictable

Who should read this | All Struts 2 developers and users
Impact of vulnerability | The attacker make a specially craft form using the predicted token that force an action to a logged-in user (CSRF).
Maximum security rating | Medium
Recommendation | Developers should immediately upgrade to Struts 2.3.20 if they use `<s:token/>` support
Affected Software | Struts 2.0.0 - Struts 2.3.16.3
Reporter | Philippe Arteau of Groupe Technologies Desjardins
CVE Identifier | CVE-2014-7809

## Problem

The attacker fetch any given form where a token is present and can predict the next value of the token used to secure form submission.

## Solution

In Struts 2.3.20 a better random generator was used to generate unpredictable values.

## Backward compatibility

No backward compatibility problems are expected.

## Workaround

Not possible when using `<s:token/>` tag - you must upgrade to the latest version.