CVE-2021-20789

Severity: medium (CVSS 6.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.9% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-07-30 · updated 2026-06-17
Weakness: CWE-601

Description

Open redirect vulnerability in GroupSession (GroupSession Free edition from ver2.2.0 to the version prior to ver5.1.0, GroupSession byCloud from ver3.0.3 to the version prior to ver5.1.0, and GroupSession ZION from ver3.0.3 to the version prior to ver5.1.0) allows a remote attacker to redirect a user to an arbitrary web site and conduct a phishing attack via a specially crafted URL.

Affected products

Japan Total System Co.,Ltd. GroupSession: from 2.20 before 5.1.0 — fixed in 5.1.0
Japan Total System Co.,Ltd. GroupSession byCloud: from 3.0.3 before 5.1.0 — fixed in 5.1.0
Japan Total System Co.,Ltd. GroupSession ZION: from 3.0.3 before 5.1.0 — fixed in 5.1.0

How to fix

Upgrade to a fixed version: Japan Total System Co.,Ltd. GroupSession 5.1.0; Japan Total System Co.,Ltd. GroupSession byCloud 5.1.0; Japan Total System Co.,Ltd. GroupSession ZION 5.1.0. Check the vendor advisory for mitigations.

References

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