A file with a long filename could have had its filename truncated to remove the valid extension, leaving a malicious extension in its place. This could potentially led to user confusion and the execution of malicious code.
*Note*: This issue was originally included in the advisories for Thunderbird 102.6, but a patch (specific to Thunderbird) was omitted, resulting in it actually being fixed in Thunderbird 102.6.1. This vulnerability affects Firefox < 108, Thunderbird < 102.6.1, Thunderbird < 102.6, and Firefox ESR < 102.6.