Joseph Bisch discovered that Irssi incorrectly handled incomplete escape codes. If a user were tricked into using malformed commands or opening malformed files, an attacker could use this issue to cause Irssi to crash, resulting in a denial of service. (CVE-2018-5205) Joseph Bisch discovered that Irssi incorrectly handled settings the channel topic without specifying a sender. A malicious IRC server could use this issue to cause Irssi to crash, resulting in a denial of service. (CVE-2018-5206) Joseph Bisch discovered that Irssi incorrectly handled incomplete variable arguments. If a user were tricked into using malformed commands or opening malformed files, an attacker could use this issue to cause Irssi to crash, resulting in a denial of service. (CVE-2018-5207) Joseph Bisch discovered that Irssi incorrectly handled completing certain strings. An attacker could use this issue to cause Irssi to crash, resulting in a denial of service, or possibly execute arbitrary code. (CVE-2018-5208)