Laptop Very Slow Lately

[Coppit]

Windows 10, Firefox. Computer usually left in Sleep mode.
It's been subjected to checks with Malwarebytes and full Norton check, CCleaner and full defrag last week.
The best short term remedy has been to shut down (usually left in Sleep mode) but just now before that ended:-
System error. Detected overflow of stack .... could potentially allow a malicious user to gain control.
Please suggest remedy. TKS

[emmie]

I have the same problem, perhaps it's your internet provider??

[Buenchico]

If, when you go into sleep mode, you leave Firefox running, you might well find that it gradually hogs more and more memory. (The same is true when you simply leave Firefox open for a long time anyway, even if you're actively using it).

I've certainly experienced similar problems. I now close Firefox whenever I'm not using it. Also, if I'm using it for any extended period of time, I remember to carry out a memory dump every so often. (To do that, type about:memory into the address bar and hit Enter. Then click on Minimize Memory Usage)