USN-4995-2: Thunderbird vulnerabilities

USN-4995-1 fixed vulnerabilities in Thunderbird. This update provides
the corresponding updates for Ubuntu 18.04 LTS.

Original advisory details:

Multiple security issues were discovered in Thunderbird. If a user were
tricked into opening a specially crafted website in a browsing context, an
attacker could potentially exploit these to cause a denial of service,
obtain sensitive information, spoof the UI, bypass security restrictions,
or execute arbitrary code. (CVE-2021-23961, CVE-2021-23981,
CVE-2021-23982, CVE-2021-23987, CVE-2021-23994, CVE-2021-23998,
CVE-2021-23999, CVE-2021-29945, CVE-2021-29946, CVE-2021-29967)

It was discovered that extensions could open popup windows with control
of the window title in some circumstances. If a user were tricked into
installing a specially crafted extension, an attacker could potentially
exploit this to spoof a website and trick the user into providing
credentials. (CVE-2021-23984)

Multiple security issues were discovered in Thunderbird's OpenPGP
integration. If a user were tricked into importing a specially crafted
key in some circumstances, an attacker could potentially exploit this
to cause a denial of service (inability to send encrypted email) or
confuse the user. (CVE-2021-23991, CVE-2021-23992, CVE-2021-23993)

A use-after-free was discovered when Responsive Design Mode was
enabled. If a user were tricked into opening a specially crafted
website with Responsive Design Mode enabled, an attacker could
potentially exploit this to cause a denial of service, or execute
arbitrary code. (CVE-2021-23995)

It was discovered that Thunderbird mishandled ftp URLs with encoded
newline characters. If a user were tricked into clicking on a specially
crafted link, an attacker could potentially exploit this to send arbitrary
FTP commands. (CVE-2021-24002)

It was discovered that Thunderbird wrote signatures to disk and read them
back during verification. A local attacker could potentially exploit this
to replace the data with another signature file. (CVE-2021-29948)

It was discovered that Thunderbird might load an alternative OTR
library. If a user were tricked into copying a specially crafted
library to one of Thunderbird's search paths, an attacker could
potentially exploit this to execute arbitrary code. (CVE-2021-29949)

It was discovered that secret keys imported into Thunderbird were
stored unencrypted. A local attacker could potentially exploit this to
obtain private keys. (CVE-2021-29956)

It was discovered that Thunderbird did not indicate when an inline signed
or encrypted message contained additional unprotected parts.
(CVE-2021-29957)