Images from a different domain can be read using a canvas object in some circumstances. This could be used to steal image data from a different site in violation of same-origin policy. This vulnerability affects Thunderbird < 60.7, Firefox < 67, and Firefox ESR < 60.7.

References

• https://nvd.nist.gov/vuln/detail/CVE-2019-9817
• https://bugzilla.mozilla.org/show_bug.cgi?id=1540221
• https://www.mozilla.org/security/advisories/mfsa2019-13
• https://www.mozilla.org/security/advisories/mfsa2019-14
• https://www.mozilla.org/security/advisories/mfsa2019-15