Update: CSL-1 is not a cosmic string.
A short addition to the discussions about the conjectured lensing by a cosmic string:
They compare the spectra of the two images - CSL-1a and CSL-1b - and show that they're identical at more than 99.9% confidence level.
Meanwhile, Mark Jackson and I have seen the positions of the other potentially lensed objects in the neighborhood of CSL-1 and we were unimpressed by their seemingly chaotic positions; one would expect that they would be kind of aligned.
A previous article was about WMAP and cosmic strings.