I'm hitting a rather significant memory leak too. My HDD started trashing and my machine became incredibly slow. At this point I noticed xfce4-sensors-plugin was using about 2Gb of RAM.
$ uptime
11:15:14 up 51 days, 18:10, 1 user, load average: 3.30, 3.91, 3.68
$ top
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
2652 user 20 0 2343876 1.865g 4968 S 0.0 7.9 71:09.88
xfce4-sensors-p
$ ps auxf
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
root 1279 0.0 0.0 309732 1312 ? SLsl Sep07 0:00
/usr/sbin/lightdm
root 1521 13.3 0.3 1407696 90544 tty7 Rsl+ Sep07 9952:48 \_
/usr/lib/xorg/Xorg :0 -seat seat0 -auth /var/run/lightdm/root/:0 -nolisten tcp
vt7 -novtswitch
root 1924 0.0 0.0 267788 624 ? Sl Sep07 0:00 \_ lightdm
--session-child 14 23
user 1988 0.0 0.0 4292 8 ? Ss Sep07 0:00 | \_
/bin/sh /etc/xdg/xfce4/xinitrc -- /etc/X11/xinit/xserverrc
user 2375 0.0 0.0 11148 176 ? Ss Sep07 0:32 | \_
/usr/bin/ssh-agent /home/user/.xsession
user 2569 0.0 0.0 345872 6188 ? Sl Sep07 6:15 | \_
xfce4-session
user 2602 0.3 0.0 421048 16400 ? Sl Sep07 295:09 |
\_ xfwm4 --display :0.0 --sm-client-id 25f8d8283-7988-4b29-a508-3819f2dea688
user 2603 0.0 0.0 362164 5796 ? Sl Sep07 0:00 |
\_ Thunar --sm-client-id 24d5a28e0-b5f9-4268-96b7-ebb4742aec3d --daemon
user 2605 0.0 0.0 457208 19264 ? Sl Sep07 17:22 |
\_ xfce4-panel --display :0.0 --sm-client-id 2f7fea66a-cc58-4e2f-bf2c-8f1068a
user 2652 0.0 7.9 2343876 1955552 ? Sl Sep07 71:09 | |
\_ /usr/lib/x86_64-linux-gnu/xfce4/panel-plugins/xfce4-sensors-plugin 30
16777254 xfce4-sensors-plugin Sensor plugin Show sensor values.
$ apt-cache policy xfce4-sensors-plugin
xfce4-sensors-plugin:
Installed: 1.2.6-1+b1
Candidate: 1.2.6-1+b1
Version table:
1.3.0-2 50
50 http://ftp.debian.org/debian sid/main amd64 Packages
*** 1.2.6-1+b1 500
500 http://ftp.debian.org/debian stretch/main amd64 Packages
100 /var/lib/dpkg/status
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