Comment 2 for bug 1766942

Confirmed the behavior with the following test from https://github.com/tmux/tmux/issues/1167#issuecomment-349040998

Run a simple/crude test in order to verify this finding:

$ tmux -L none -f /dev/null new-session -s leaky-tmux-test 'tmux set-option -w -g pane-border-status top; tmux pipe-pane "cat>/tmp/leaky-tmux-test.log"; p=${TMUX#*,}; p=${p%,*}; s=0; j=0; echo "ITER: RSZ"; while [ $j -lt 6000 ] ; do j=$((j+1)); n=$(ps hwo rsz $p); printf "\e]2;%d: %d\e\\\\\r%4d: %d" $j $n $j $n; [ $s -ne $n ] && { echo; s=$n; }; done'
[exited]
$ cat /tmp/leaky-tmux-test.log ; echo
ITER: RSZ
   1: 3512
1993: 3568
3650: 3696
5279: 3824
6000: 3824

To compare, run it without tmux set-option -w -g pane-border-status top:

$ tmux -L none -f /dev/null new-session -s leaky-tmux-test 'tmux pipe-pane "cat>/tmp/leaky-tmux-test.log"; p=${TMUX#*,}; p=${p%,*}; s=0; j=0; echo "ITER: RSZ"; while [ $j -lt 6000 ] ; do j=$((j+1)); n=$(ps hwo rsz $p); printf "\e]2;%d: %d\e\\\\\r%4d: %d" $j $n $j $n; [ $s -ne $n ] && { echo; s=$n; }; done'
[exited]
$ cat /tmp/leaky-tmux-test.log ; echo
ITER: RSZ
   1: 3492
6000: 3492

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Tested this with tmux 2.7 (in cosmic) and verified it fixed. Bionic is still affected.