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CVE-2021-23984 Moderate

CVE-2021-23984

A malicious extension could have opened a popup window lacking an address bar. The title of the popup lacking an address bar should not be fully controllable, but in this situation was. This could have been used to spoof a website and attempt to trick the user into providing credentials. This vulnerability affects Firefox ESR < 78.9, Firefox < 87, and Thunderbird < 78.9.

Exploit probability 1.1%
Published March 31, 2021
Required by Not available
Last source change April 16, 2026

02 / AFFECTED SOFTWARE

Affected packages

Unknown Unknown

03 / CONNECTIONS

Connected vulnerabilities

04 / EVIDENCE

Source records

Open Source Vulnerabilities CVE-2021-23984

A malicious extension could have opened a popup window lacking an address bar. The title of the popup lacking an address bar should not be fully controllable, but in this situation was. This could have been used to spoof a website and attempt to trick the user into providing credentials. This vulnerability affects Firefox ESR < 78.9, Firefox < 87, and Thunderbird < 78.9.

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05 / REFERENCES

Further evidence