The vulnerabilities story seems like storm in a tea cup - old software basically being discontinued (with clients having been advised previously as such), so no big deal. Like continuing using XP on your PC.
I think most of the recent fall in s/p is the court case as guntoncliff suggests. But Friday's fall seems odd - maybe some people saw the vulnerabilities story and were needlessly spooked. But more likely to be a response to possible interest rate rise I'd think (which makes some high yield shares less attractive and also makes new/re-servicing debt cost more).
Anyway, sitting on paper loss but will wait for court case when, if in Inmarsat's favour, I expect s/p to rocket.