A recent article about the telescope states (emphasis mine):
Unlike Hubble, which orbits the Earth at about 340 miles of altitude, Webb will be sent almost a million miles into space, at a specific location called "L2." It's one of five so-called Lagrange points, specific areas of stability where the gravity from the Earth and the Sun balances out in such a way that putting an object there keeps it in a fixed position relative to the two celestial bodies. The telescope will therefore hitch a ride through space without the need for engines or propulsion, while enjoying an unobstructed view.
The same article also notes:
To protect itself from the warmth of the Sun, the mirror will sit on a 70-ft sunshield -- as long as a tennis court -- made of a special heat-resistant material. It looks like a giant kite and it will keep the mirror at a gelid -370°F, or -223°C, nearly three times colder than the coldest temperature ever recorded on Earth.
From which I gather that the telescope is designed to sit at the L2 Lagrange point while using minimal (if any) propulsion to maintain its position and orientation. However the second paragraph makes it sound like the telescope will sport what essentially sounds like a (quite small) solar sail.
So the question is, if the 'sunshield' is always positioned between the telescope and the sun and therefore always being irradiated by the sun, won't that over time generate enough thrust the push the telescope out of position or alignment, particularly if it's a truly passive system and not able to counteract with its own engines/maneuvering thrusters?