There is an out-of-bounds write in checkType located in etc.c in w3m 0.5.3. It can be triggered by sending a crafted HTML file to the w3m binary. It allows an attacker to cause Denial of Service or possibly have unspecified other impact.
github.com/tats/w3m/issues/242
lists.debian.org/debian-lts-announce/2023/08/msg00030.html
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