System Information
Operating system: Windows-10-10.0.19041-SP0 64 Bits
Graphics card: GeForce RTX 2080 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 452.06

Blender Version
Broken: version: 2.92.0 Alpha, branch: master, commit date: 2021-01-12 20:03, hash: rB719bea0d6d06

Short description of error
In this simple example (file available below) I created a vertex group that i used as an attr in a geonode modifier then remove some weight using an attr math node, at first glance everything seem to work fine. But on some condition (entering a field then hit esc, or evaluating the depsgraph with python or else?) the node keep re-evaluating itself, this can be repeated indefinitely.

So the attr workflow seems to re-evaluate the attr it produces (feedback loop) This is quite an unexpected workflow-breaking behavior, it's the first time that a modifier re-evaluate something that it produces (for example the vgedit modifier only evaluate the vertex-group initially, and don't re-evaluate the resulting vertex-group) Somehow this is not making any crashes as the re-evaluation is not continuous. blender is re-evaluating only on some conditions, not sure why and when this re-evaluation occurs?

this is significantly breaking the attr workflow.
here's a gif illustrating the issue

Exact steps for others to reproduce the error
Blank file:

• Create a new vertex group on a subdivided plane and paint something
• Create a new geonode modifier, and add a node that will change the vertex-group weight.
• Evaluating the mesh with his modifiers using python or entering and quitting the B arg of the math node will trigger a re-evaluation of the node. this re-evaluation may be triggered by some other events.

Use file below:

• just enter in the edition of the "B" FloatProperty of the AttributeMath node then hit ESC witouth changing any values, this is one way to trigger a re-evaluation of the node resulting in a change of this vertex-group

note that entering edit mode will reset the weight