Mozilla released Thunderbird 188.8.131.52 and the following security issues have been fixed.
Upgrade PNG library to fix memory safety hazards
Google security researcher Tavis Ormandy reported several memory safety hazards to the libpng project, an external library used by Mozilla to render PNG images. These vulnerabilities could be used by a malicious website to crash a victim’s browser and potentially execute arbitrary code on their computer. libpng was upgraded to version 1.2.35 which containis fixes for these flaws.
XML data theft via RDFXMLDataSource and cross-domain redirect
Mozilla security researcher Georgi Guninski reported that a website could use nsIRDFService and a cross-domain redirect to steal arbitrary XML data from another domain, a violation of the same-origin policy. This vulnerability could be used by a malicious website to steal private data from users authenticated to the redirected website.
Crashes with evidence of memory corruption (rv:184.108.40.206)
Mozilla developers identified and fixed several stability bugs in the browser engine used in Firefox and other Mozilla-based products. Some of these crashes showed evidence of memory corruption under certain circumstances and we presume that with enough effort at least some of these could be exploited to run arbitrary code.