The Mozilla Foundation's Security Advisory describes the following issue: A crafted HTML email using mailbox:/// links can trigger automatic, unsolicited downloads of .pdf files to the user's desktop or home directory without prompting, even if auto-saving is disabled. This behavior can be abused to fill the disk with garbage data, such as using /dev/urandom on Linux, or to leak Windows credentials via SMB links when the email is viewed in HTML mode. While user interaction is required to download the .pdf file, visual obfuscation can conceal the download trigger. Viewing the email in HTML mode is enough to load external content.

Rejected reason: This CVE was marked as fixed, but due to other code landing - was not actually fixed. It was subsequently fixed in CVE-2025-5986.

A crafted HTML email using mailbox:/// links can trigger automatic, unsolicited downloads of .pdf files to the user's desktop or home directory without prompting, even if auto-saving is disabled. This behavior can be abused to fill the disk with garbage data (e.g. using /dev/urandom on Linux) or to leak Windows credentials via SMB links when the email is viewed in HTML mode. While user interaction is required to download the .pdf file, visual obfuscation can conceal the download trigger. Viewing the email in HTML mode is enough to load external content. This vulnerability affects Thunderbird < 128.10.1 and Thunderbird < 138.0.1.

Уязвимость почтового клиента Thunderbird, связанная с недостаточной защитой служебных данных, позволяющая нарушителю загружать произвольные файлы

Security update for MozillaThunderbird

Security update for MozillaThunderbird

ELSA-2025-8203: thunderbird security update (IMPORTANT)

ELSA-2025-8756: thunderbird security update (IMPORTANT)